The G30 is not offered compensated. The new G30's also come with a rail, my old G30 doesn't.
I own both pistols with the USPc being in 9mm. They are both great guns. If I absolutely had to pick one, it would be the G30. That is the most accurate gun that I have shot.
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www.cdnninvestments.com
www.ordnanceoutsellers.com
www.topglock.com
They are all reputable dealers to me.
My G30 has the following modifications done: 3.5# connector, extended slide release, Mepro's. My USPc's only modifications are Mepro's.
Beware of the G30, some people think that the gun is a little too wide. Even though I have small hands, it fits my hand perfectly. I have better trigger control with my G30 than I do with my USPc or my P229. And don't let the recoil of the .45 intimidate you. The G30 recoil is extremely manageable, I'm 5'6", 130 lbs. and I have no problems with recoil on the G30.
The G30 is a little bit more concealable to me than the USPc. When I carry my G30, it's usually in a Sidearmor IWB and the USPc is in a High Noon OWB. Another great thing about the G30, and about the compact and sub-compact Glocks, is that they accept the magazines from their big brothers. I carry the standard 10 round mag inside the gun with 2-13 round G21 mags as backup. Downside to that is the weight of the .45 but that is with any .45.
The USPc has it's own benefits. For one, it is lightweight and if you have to carry the gun for long periods of time, the weight will make a difference. Then again, both are lighter than my P229. But I also have a shoulder holster to balance out the weight on my P229.
My suggestion would be to shoot both of them, they are both totally different animals. Keep in mind that if you get the V1 on the USPc (one of the most common variants), you can carry the gun cocked and locked. I don't carry it locked and cocked, however.
Just do what I did and get both of them, you won't regret it!