Kermit,
As you know, these are both truly outstanding autoloaders. I own a Sig P-220 and an H&K USP Tactical, the Expert's "brother". I admire the H&K's design, reliability, rugged durability, and its decocker/safety system (in variant #1), but if I were compelled to choose just one of these two superb semiautomatics, I'd pick the Sig.