Cedar,
You did not specify if you wanted to add a front or rear snowblower.
You also did not say how long your driveway is or if it is steep or flat.
If your drive is over 200-250 ft, you might want a front blower. I would not want to back up that far with my neck twisted. (many disc about that here prev.)
If you decide on a front blower, you may want to go with the 7610, especially if you have any sort of hill on your drive. It'll take all of the HP you get muster to snowblow uphill at a decent speed. (not crawling)
Either 7510/7610 will run a 60" MMM fine. If you want/need a 72"RFM, than again, the 7610 would be better for this.
I pondered the same thing as you. The 7610 w/352 loader cost $800 more than the 7510 w/302. I also got the front snowblower. I appreciate the extra HP when snowblowing uphill (my 1000 ft drive), though it still does bog down at times. And I REALLY use the extra capacity of the loader. (And I didn't want a loader originally. Then dealer talked me into a LA272 with the 7510, then the LA302 with the 7610, and finally a LA 352 and 7610) Glad I went with the 7610 and LA352.
BTW: Check around and compare dealers. I got my 7610/LA352/60"MMM for a little LESS money than the first dealer quoted me for a 7510/LA272/60"MMM !! True! So in reality, after a little looking around, the extra HP and larger loader cost me nothing.