I believe that the old spin milled wedges are not allowed for tournament play. The Northern California Golf Association made that decision some time ago, its why I bought the SM4's in the first place. If you don't play tournaments than it doesn't matter. If you do play tournaments, it would be a good idea to check with the USGA or regional golf association. 

I feel like the SM4s are better.  It use to be the Spin Milled were so cheap, they were an attractive option if you didn't mind the non-conforming grooves.  But now that SM4s have dropped so low in price, I would just go with them.

SM4 for sure. Better distance and trajectory control. Another benefit is your golf ball will last a whole round. 

 OP was asking about SM2 vs SM4.