You are correct, all of those models use the same frame (the Glock 30/38 have a wider slide to support the .45 caliber) the rest have the same slide dimensions.
I would say the biggest difference between them is felt recoil. The G19 9mm is a pretty tame gun, easy to see why it's so popular. The .40 and .357 Sig models have more felt recoil and in my opinion don't absorb the recoil as well as some of their competitors.
I am a fan of the Gen 5 19 myself, I like the straight grip without finger grooves and widened magwell. I also shoot the Gen 5 the best. I'm not sure if it's the "marksman" barrel, or improved trigger of the Gen 5, but I was pleasantly surprised the first time I tried one.

the dimensions are the same or very similar as you state. In the compacts, the smaller dimensions and lighter weight make the 9mm the best choice caliber wise. It will give the best combination of power, control-ability and capacity in the smaller packages. This is my experience with smaller hand guns. You can become proficient with just about any caliber with practice but. i feel that learning curve will be shorter with the 9mm plus it will cost less for ammunition for even more overall cost savings.

Hi Eldridge, the dimensions are the same or very similar as you state. In the compacts, the smaller dimensions and lighter weight make the 9mm the best choice caliber wise. It will give the best combination of power, control-ability and capacity in the smaller packages. This is my experience with smaller hand guns. You can become proficient with just about any caliber with practice but. i feel that learning curve will be shorter with the 9mm plus it will cost less for ammunition for even more overall cost savings.

Eldridge, the dimensions are the same or very similar as you state. In the compacts, the smaller dimensions and lighter weight make the 9mm the best choice caliber wise. It will give the best combination of power, control-ability and capacity in the smaller packages. This is my experience with smaller hand guns. You can become proficient with just about any caliber with practice but. i feel that learning curve will be shorter with the 9mm plus it will cost less for ammunition for even more overall cost savings.