On duty I wear a G22 as a primary sidearm and a G27 as a BUG daily. Most of the time, the G27 is on my ankle. Less than ideal, but I already have cuffs, badge, spare mag, and a light on my belt. The G27 is too large for me to carry in a pocket in 99% of my clothes. The good thing about ankle carry is that it can be the easiest and quickest gun when seated in a car.
On days when I wear shorts (usually that’s off duty), I either wear the G27 in a crossdraw position or I go w/o a BUG. I am purchasing an M&P340 for situations such as this. Truth be told, I’d probably carry the j-frame on duty if that were an option.
I have an M&P9C and love the gun! It’s about the same size as my G27, but thinner. It might be more easily carried in a pocket. If you wear cargo pants a lot, there are pocket holsters for these weapons specifically designed to work well there.
Everyone seems to have covered the hows and whys of a BUG. I came from the military where “2 is 1, and 1 is none.” That said, I do sometimes go w/o the BUG. Don’t like to go w/o, and know I should have 2 with me, but that’s real life. It’s up to you if you are willing to dress around 2 guns or just 1.
As for not having identical platforms, such as going from an M&P to a snubbie… I think you’ll be fine under stress. The only time I see that becoming an issue is when you introduce a manual safety or drastically different manual of arms into 1 of the weapons (chiefly the BUG).
I work with officers who use pocket carry for Kel Tecs and Kahrs. They seem happy. My preference for a BUG is a revolver simply because it isn’t prone to being pushed out of battery if your attacker is fighting with you (hands on). My G27 will get one round off, if that under those conditions. A wheel gun will fire all it has. Additionally, should I be in a spot where I need to arm someone with me by giving them my BUG… a DAO revolver seems pretty “idiot proof” regardless of that person’s experience handling weapons.
Finally (this post is longer than I originally intended), I am planning to purchase one of these: http://www.desbiensgunleather.com/wp-content/uploads/2009/10/covertbadger.jpg
Spankavelli was kind enough to share with me where he got his.
They also offer a crossdraw style: http://www.desbiensgunleather.com/wp-content/uploads/2009/10/covertbadger2.jpg
Good luck whatever you decide. It can be a PITA to carry 1 sometimes, let alone 2. But when you need it, nothing else will do.