US2H is a little inferior to the UD2H. the D stands for Durable. All UD series boards come with 100% solid capacitors, which have a much longer life than the electrolytic ones. The US2H has solid capacitors only around the CPU AFAIK, and the rest of the board has the standard electrolytic ones. So technically, the UD board should last longer, overclock better and also will be able to withstand higher temperatures. AFAIK, solid caps don't leak as easily as the electrolytic ones. Please feel free to correct me if I am wrong anywhere.