I try to carry the same thing, day in and day out, and I try to carry "as much gun" as I can comfortably conceal. However, I've found that those two ideas don't always play well together, so I've ended up with three carry pistols.
1. Small -- Ruger LCR -- It's my "shorts and 7 am Home Depot run" pistol.
2. Medium -- S&W Shield -- I carry this one the most, as I can conceal it with my standard wardrobe with a minimum of fuss, and it meets all of my other CC criteria.
3. Large -- Glock 19 -- This used to be my EDC, and I carried it far more than anything else. It's been downgrades somewhat since I got my Shield. It's for cold weather and, well, any other day that I feel like carrying something bigger than the Shield.
The real requirement for me in all of this is that all three pistols are of the "point and shoot" variety. No thumb safeties. Some folks like a thumb safety, some don't. What I'd suggest (with the caveat that I'm a bona fide pencil pusher) is that you avoid mixing them in your carry rotation. Avoid having one pistol with a thumb safety and one without.