I have shot the shield and M&P compact, both in .40 and would take the compact any day over the shield. Get 3 more rounds in the standard mag, and to me it just feels like it fits better in the hand. The best part about the compact is the ability to run full sized mags in it as well (just like glock), with the grip sleeve or not, you still can get 12rds in a compact, which is nice. Also the shield, in .40, because of the smaller grip/frame, its definitely a little on the snappy side. Might be more tame in 9mm, but I couldn't speak to that.
Quality wise, its a smith. Great gun, will last a long time. Just size wise its not for me.