Some Schirmers are perfectly good, but a lot of them were done a long time ago and reflect the tastes of their period in all sorts of ways. Perhaps the worst feature of editions from long ago is that editors tended to add all sorts of markings, including some quite significant dynamics, even tempo markings, without indicating that the addition was editorial. You never really know what you're getting until you do a little research. For instance, the Schirmer editions of the Bach-Busoni Chaconne, and of the Rachmaninov 3rd piano concerto (both of which I own) are facsimile the same as the Breitkopf and original (whatever it was - Gutheil? - can't remember offhand) respectively. Given they are cheap, printed on OK paper and with an OK binding, they are a good buy.