Been shooting cap and ball revolvers for about 40 years.
I would not buy a brass frame. Not only are they less resistant to higher pressures, brass-framed revolvers tend to be less better made.
Their fit and finish is often not as good as the steel-framed guns. It's as though the factories don't put the work into brass-framed guns, and that's why they're sold at a cheaper price.
Spend a little extra money and get a steel-framed gun.
I have Uberti, Pietta, Colt 2nd generation, ASM and Cimmaron guns.
The Colt 2nd generation, Uberti and Cimmaron are by far the best made.
My understanding is that Cimmaron purchases the best Ubertis, and then slicks them up a bit. The gaudy Italian proof marks found on Ubertis and other Italian-made guns are not as evident on Cimmaron guns. They're generally hid under the rammer, apparently by request from Cimmaron.
Cimmaron roll-marks its own name and address, in old-timey script, along the top of the barrel. It looks more authentic that way.
Uberti is very well made too.
The Colt 2nd generation is the standard by which reproductions are judged. It is not considered a reproduction, but a reissue. The frame and a few other parts were made by Uberti in Italy, then shipped to Colt for finishing.
Yet, detractors refer to them as "Italian made" and "Spaghetti Colts." Funny how these same detractors never mention "Limey Colts" made in London in the 1850s, or "Sushi Winchesters or Brownings" made by Miroku of Japan.
Ah well ...
Go with Uberti or Cimmaron if you can afford it. You'll end up with a revolver that, properly cared for, will last for generations.
Colt or Remington design? I shoot both. The Colt is far better balanced. It will also shoot longer before fouling causes the cylinder to drag: the Colt has a larger diameter cylinder pin, upon which the cylinder revolves. It is also machined with grooves to hold lubricant, and to allow someplace for fouling to collect.
The Remington has a small diameter cylinder pin, smooth, providing no place for grease to remain or fouling to collect.
The Colt and Remington are amply strong for black powder and its substitutes. The Remington is stronger than the Colt, if you foolishly try to exceed charges listed for the stronger Hodgdon 777, but staying within recommended loads of 777 (see the Hodgdon site) will keep both revolvers operating without accelerated wear.
The Colt 1851 and 1861 Navies have been proclaimed as one of the best-balanced revolvers ever made. The Remington is not nearly as well balanced, some find it very ill-balanced. It feels clunky in my hand, in both the .36 and .44 version, but it is accurate.
The Colt is far more forgiving if you load too much in a chamber and can't seat the ball deep enough for the cylinder to clear the barrel. Pop off the barrel, hold the cylinder back by hand, carefully cock it, and fire the protruding ball out of the chamber.
The Remington will require you to remove the nipple, scrape out the excess powder with a stick or brass pick (something that can't produce a spark), replace the nipple, seat the ball deeper and shoot it out.
The Colt is more prone to get cap fragments in its mechanism, tying it up. Some shooters reduce this tendency by carefully polishing the face of the hammer to slick smoothness, so the hammer can't grasp cap fragments.
The Remington is not so prone to pull caps back and drop them into the action, but it is more likely to get caps stuck between the frame and cylinder, tying it up.
By now, you're thoroughly confused.
Frankly, it's a matter of what feels good in your hand and appeals to your eye.
For newcomers, if they can afford it, I suggest a stainless steel Remington in .44 caliber (to my knowledge, no one makes a stainless steel .36 Remington).
I like the .36 caliber, but I also swear by the use of .380" diameter balls, not the recommended .375 inch. Alas, .380 balls are not usually available on the shelf, and require special ordering or casting your own.
However, with the .44 caliber, I recommend .454 inch balls. These are commonly available.
I don't use a separate loading device. I don't see the need for one. Either revolver is amply strong to withstand any sane seating pressure applied to balls or conical bullets with its attendant rammer.
Folks got along fine with the revolver's rammer for 150 years or so. I just don't see the need for more gear.
If you can find it, or order it, use real black powder. FFFG grade is preferred, but FFG will do in a pinch. It's the most accurate propellant I've found.
Felt wads soaked in a stiff, all-natural (non petroleum-based) lubricant such as SPG, Lyman Black Gold, lard, a mix of beeswax and lard, or the homemade lubricant named after me -- Gatofeo No. 1 -- are preferred between ball and powder. Hard felt is needed. You can buy Wonder Wads and soak them, but they cost about a dime apiece. If you buy hard, wool felt from Durofelt, off the net, and a punch, you can make your own wads for a penny or less.
In summation: Remington .44 caliber. Stainless steel if you can afford it. Avoid any and all brass frame guns. Use real black powder. The choice of Colt or Remington is a personal choice because both designs have benefits and failings. Don't feel obligated to purchase a separate loading device because the revolver's rammer works just fine.
Also, wear eye and ear protection. Never let anyone stand to the side when firing. While firing, keep all powder and caps behind you, out of the range of sparks. Keep your fingers away from the front of the cylinder when placing caps on the nipples. Don't judge the revolver's accuracy until you've put at least 100 rounds through it; it sometimes needs time to settle in (I can't explain this last statement, but I've seen it happen with some revolvers).
Be safe. Have fun. Carry more than a few grains of salt for all the suggestions and historical lore you'll hear at the range. A fair portion of it is fabrication, guesswork, fable or bragging.