It's true, the .40 is popular by region, but the main reason .40 ammo has been more available, is due to the majority of the 9mm and .45 ACP ammo has been going to the Gulf. Federal also re-tooled their ammo production lines, which has not helped, Winchester took up the slack in the military orders, add to this all the hording, new owners trying to find feed for their new purchases, alot of them being horders, panic buying started by the election issues, again, alot of the new buyers being in this crowd, and we had the shortage. In my location, the .40 is popular, however, there has always been ammo available, while .380 is all but non-existant, 9mm, and .45ACP, mostly CCI Balzer, and import stuff(MagTech, PMC, etc.), and Rem. UMC has trickled in here and there, only to be bought up as son as the horders found it.
Go with the .40, it's a good round, my go to pistol is a Glock 22, and has a good reputaion with law enforcement, almost all of the top defensive loads are available in the .40, Hornanday TAP being one of the top picks. There alot of good choices in makes and models. If you are on a tight budget, the S&WE Sigma series is a good pistol for the price, had one years ago, and it was one of the best I owned.