I have both. I own an XD 9 service model (4"barrel) and a M&P 9 (4.25'' barrel).
Obviously, if you are price based and wanting it right away, the XD is the gun for you. M&Ps seem to be the 'hot' seller right now , as were the XD's 4-5 years ago. But I think every gun on the counter is a hot seller given the talk on capital hill.
Both guns are reliable, shoot straight, and are overall great guns. I personally like the M&P better. Why? It comes down to the ergonomics of the gun to "my" hand. Which in turn, makes it a better gun for me to shoot and me a better shooter. Yeah, there are features here and there between the two- but in the end it comes down to ergos. And your wallet of course! Lets be honest an HK P30 fits like a glove, but not over my mortgage payment!
Hopefully you've shot both of them or at least handled them both at the gun counter. If the springfield feels good in the hand and you feel comfortable with the grip/trigger/and features. Take it. But if you put the M&P in your hand and it feels at all better, even just a little bit- do yourself a favor and wait a month. Save an extra 100 bucks, and get the M&P.
If you were to put the guns on a comparison chart of their features and builds- the M&P would win. But when its in your hand- its really your personal preference. IMHO its going to, and should, come down to that.