i have playmags and magnatileis for a few years already. the quality is the same. they hold up the same and work the same. the only difference is that the original magnatiles hold the magnets together better. but they both really work the same.
also, one set isn't enough. once you're buying you need a few since 100 pcs makes something pretty small. so if it'll make a difference i would rather buy playmags and buy 2 sets reather than one set of magnatiles.