Well, obviously a complicated question with thousands of possible answers and no right answer.
But I will say a couple of things, which I've repeated many times before, if you will take advice from a 44 year old who's been carrying since 1987...
1. First, the answer depends most highly upon your METHOD of carry (what it will be). The first sub-choice there is, Is it going to be the type of carry which (a) DOES, or (b) DOES not depend upon having a covering garment - As for (a), where a covering garment is required, where you live up north, this will work well in 3 of 4 seasons but not summer. Examples of (a) are strong-side belt-carry OWB, strong-side belt-carry IWB non-tuckable, cross-draw OWB, cross-draw IWB, shoulder rig. Examples of (b) are "Smartcarry", pocket carry, purse/man-purse carry or similar, fanny pack, ankle carry, strong-side belt carry IWB with "Tuckable". Then which of those specific choices is it going to be? Or which oneS if more than one? Generally, single stacks are better for ALL types except the OWB varieties under type (a) - where you have a covering garment, or purse/satchel carry. In those latter cases why not go with a 2-stack? You may end up doing what I and a lot of people do - get 2 guns for concealed carry (at least): one tiny single-stack one ("subcompact") for pocket carry or smartcarry for the late spring / summer / early fall, and one larger one ("compact" or "full-sized") for OWB or IWB belt carry for late fall / winter / early spring.
For the former category (summer carry), I'm looking to the Boberg XR9-L or Remington R51 or the new Walther slim one next (and have tried many different ones in that role in the past, including various Kahrs and a Taurus 709 SLIM - these were my favorites in that role so far).
For the latter (winter carry), I'm using a CZ 85 combat in 9x19 and happy with that, although I plan to get a C-Bob 1911 in 9x19 later for winter carry. And there are myriads of good choices for that role.
2. Shoot a lot of them by renting at range if you can before deciding - like others have said. Yes, I agree.
3. Very generally speaking, after owning quite a few, I gravitate toward quality metal guns: Specifically, CZ75 family & clones, BHPs & clones, 1911s, Sig Classic P series, and metal Kahrs -oh and believe it or not, Bersas. In plastic guns, I like Kahrs and Walthers and CZs and that's about it. XDs aren't bad. HKs are very good but oh so pricey. But admittedly, I've not tried all of them or anywhere near close to all of them. Glocks are junk. Ignore that advice you hear incessantly recommending them. I say again, JUNK (not on an absolute scale but at least relative to their price - they should be *maybe* $100 more than a Hi-point). And yes, I've had a bunch of them so I speak from experience. Yeah, yeah, attack me, I know - I'm entitled to my opinion, koolaid pervasiveness notwithstanding. Bottom line, if not on a tight budget, you can NOT go wrong getting a metal CZ or 1911 or Kahr (or Sig Classic P or BHP). If on a tight budget, look at the Bersa or Tri-Star CZ75 clone or other CZ75 clones (Tanfoglio Witness, etc). If you really want a lighter weight plastic framed gun, take a good look at offerings from Walther. But there are several other good options too. You also need to take into account which action type you like and prefer (or guess or THINK that you might like and prefer best)- SAO, DA/SA, true DAO, pre-sprung DAO, etc. This too depends upon method of carry. An SAO like a 1911 or BHP, for example is fine for OWB or IWB winter carry, but I want a true DAO or stiff pre-sprung DAO like a Kahr for crotch carry (i.e. smartcarry).
So the biggest thing to answer is, what will your method of carry be? Which I know is hard to answer without having carried before. But if it's smartcarrry, the answer is very different from strong-side OWB with covering garment, for example.
Chambering - doesn't matter - whatever floats your boat - pick one of the big 3 for starters, probably: 9x19mm, .40 S&W, or .45 acp. Maybe even 10mm if you run with 1911. They all have pros and cons. Oh, well, doesn't matter, EXCEPT do NOT get a .380. In my opinion, no need for this chambering at all any more except for the most extreme recoil-sensitive cases. It's both more expensive and weaker than 9x19mm, and the guns aren't any smaller, so why?
Oh, revolvers... I'm not a fan for concealed carry. Love revolvers for other uses like woods carry, but not for concealed carry, for two reason. Bulk of cylinder being one. PM me if you want more info on this. Having said that, a revolver *may* suit you to a "T", particularly if the type of carry is man-bag/satchel, fanny pack, or strong side belt OWB.
Oh, and as always, so much depends upon budget... Budget is so important. Answer these questions and I can help you a lot better:
1. You going to run with ONE gun or two for all concealed carry, year round?
2. Budget for the gun (or budget for both guns if the answer above is two), and are you willing to buy used, or new only?
3. What do you think your method of carry will be? Will you pick one method for year-round (like smartcarry), or two methods - one for summer and one for winter, and if so which? And if the answer is two methods, go back to question #1 again and tell us, do you want both methods to be able to accommodate your one and only handgun, or are you willing to get two - one for each method?
4. Do you think you have any action type preference: SAO, DA/SA, true DAO, pre-sprung DAO, revolver? If not, can you at least rule OUT any of these? Can you say, "I like any action type EXCEPT SAO" or "I like any action type EXCEPT revolver or true DAO" ?? Something like that?
5. Finally, not quite as important, but still important, what would you guess is the breakdown of use, roughly, such as say, for example: "100% concealed carry" or "80% concealed carry, 20% home defense", or "30% concealed carry, 60% home defense, and 10% fun range gun", etc.?
Obviously, answering open carry is a lot simpler than answering concealed carry. Still lots of choices, but not nearly as complicated as concealed carry. You've got a lot of inter-dependent factors like budget, carry method, preferred action, preferred brands, if any, preferred frame material (steel, alum, or plastic?), chambering choice, etc. For example on chambering choice, if you do happen to want 10mm or .357 sig, this greatly limits your choices, and is almost ruled out for pocket or smartcarry or other "deep concalment" (like tuckable IWB). In 10mm new market options, if you avoid overpriced junk, the only thing you've got is Tanfoglio and 1911s (and another half dozen options used including SW revolvers), but these are much much better suited to strongside belt OWB carry (well, ok, the 1911 is suited for IWB as well but not really smartcarry or pocket carry). But then what are you going to do in the summer? Wear a jacket over your t-shirt in 90 degree heat? Just not carry in the summer? Or what?
Big picture, without knowing more, if you want just a flat-out "do X, Y, and Z" recommendation: I'd say get two guns and two carry rigs ASAP. Get the first one first since summer is coming up now:
1. Get a SmartCarry holster for the summer (or "always carry"), and put in it either a Kahr PM9 or CM9 if you want light, or a Kahr MK9 or Rohrbaugh R9 if it doesn't have to be super light. Or a Taurus 709 SLIM if on a tight budget. If you always wear khakis and slacks not jeans, then you can sub out a good pocket holster for the smartcarry rig.
2. Get a CZ75 or 85 full-sized in 9x19 or .40 sw, or CZ 97 in .45 acp (or BHP or Sig or 1911 in chambering of your choice....), and get a quality leather holster with kydex lining for strong-side belt OWB carry. Be prepared to really shop around online to find a great holster that fits a CZ. Now, if you do NOT want to search the nooks and crannies for the right holster for a CZ, this is where you decide to get a 1911 and be done with it (either full-sized or commander or C-Bob or "compact" - commander slide/officer grip), since there are a million and one 1911 holster choices. Or with Sig Classic P series, quite a few too. [What I did for my CZ85 was to find a fantastic leather with kydex holster made for a 1911 and re-form it to my CZ by heating and re-heating the kydex inner until it formed around the CZ. Then I used epoxy and a release agent on the gun like you would a rifle bedding job to make it fit like the proverbial glove. But I digress...]
Oh, and get two or three carry belts from Looper leather after you get rig #2.
