Body size is a factor in what you can conceal. I'm a pretty slim build, and around 6' in height. I carry a Glock 26, and don't ever have to "dress around the gun." I wear what I want and the gun hides.

I have concealed a Sig P226 and a Glock 34 before, but I have to plan what I wear in order to hide a gun that big reliably. I hate doing that, so the Glock 26 does really well for me.

I also carry in just slacks and a dress shirt all the time. It's a piece of cake if you have the right setup, mainly a low-profile tuck able holster. Getting a tuck able holster is a must, and if you are slim, you need to have a fairly small gun - my G26 is only noticeable by a single black belt loop to a very well trained eye that is looking for an extra belt loop over my right hip - I carry inside the waistband at 4:00. Ankle carry is a possibility with a small gun and good holster - but I hate the tactical disadvantage of ankle carry and only do it when it is an absolute necessity, almost never for me.

I've fiddled around with a few guns and holster combos until I settled on the Glock 26 with a Raven concealment vanguard II holster. Unless I am on a commercial aircraft without permission to carry, I'm armed - in all types of attire. The G26 + Vanguard II has been pretty much all I've carried for the last 2 years.