The USPc is what it is, an awesome weapon. The P2000 is an evolution of the USPc, introducing interchangeable backstraps. The P30 in yet, another evolution of the tried and true USP line, adding interchangeable backstraps, side plates, and a pic rail.
Either one will serve you well and as for the claim of being unreliable, take that with a grain of salt. If you shoot enough, you'll have a failure on any platform. I've even had failures to feed on my USPc stainless recently, and this failure was linked to a new 10-round magazine.
Of the ten HK pistols I own, I've documented four failures on all of them, firing an estimated 50,000 rounds over the years. Not a bad track record. I couldn't say that about my G23 or my G27 when I owned them. Heck, my G27 surpassed my entire HK failure rate on a single range trip.
Buy what fits you the best.