I am a Glock fanatic, and my favorite Glocks are the .45's and the .357's. The Glock 30 is the "excaliber" of Glocks, in most people's opinion. The Glock 32 is a close second, or maybe better depending on what day you ask me
. Both are extremely accurate. I mean EXTREMELY accurate! Tack drivers! As accurate as ANY other compact combat pistol you could put them against, no matter what cost, IMO, and I have owned most all of them.
Regarding the .40, I like the round, but I like the .357 Glock better.
I like the .357 better than the .40 because it has a "fully" supported chamber, thicker brass web, a thicker barrel, is more accurate, is flatter shooting, more velocity, more energy, holds one more extra round in the pre-ban mags, and is more reliable among other things.
If the .357 goes sour, you can always buy a .40 barrel, but .357 Glock barrels are few and far between, if they exist at all without a gun attached.
.357 Sig ammo is now about 50 cents higher per box than .40 ammo, so cost is not the concern.
.357 has had a stellar record in street shootings so far, and seems to be catching on very strongly, so I do not see it going anywhere but up in popularity. But, if all else, you can always buy a .40 barrel and be able to shoot BOTH calibers.
Ps- If only the Glock 30 had rails, I would consider it to be the ONLY Glock for me. About the only reason I like my Glock 32 on any given day more than my Glock 30, is because it has rails on it that I can mount my M3 light to. I keep my M3 light attached whenever possible.