Glock got its reputation when they were the only kid on the block as far as rugged poly guns is concerned. They were very public about all of their horrific tests they put their guns through and it is a reputation well earned. However, they are not an only child anymore in the realm of rugged dependable polymer pistols. Other companies have stepped up and made pistols that are just as durable, just as reliable. Smith & Wesson is one of those companies. They learned ALOT from their Sigma line which smacked of being a half-measure Glock ripoff, went back to the drawing board and delivered in spades on the M&P line.
The M&P line had some embarassing issues with dropping mags in their first run of pistols. They remidied this within months, and haven't had the problem since.
Either way you go, you're buying a winner.