I'd suggest the SP and build It how you want it with the money you save. I'm the type of rider that came from a race sled, ripping snocross tracks for fun, hitting road gaps, and riding some ramps back in the day. This was around 8 years ago. Took a few years off and now back in it to have fun in the trees. I ride aggressive...love to ride the whooped out trail as hard as I can on the way to our playing spots in the trees. Once we get to our riding spots, it's a day of tight tree lines and jumping off of any natural feature we can find.
I started the season on a 2015 146 Freeride. I installed grip n rip braces, removed the mtn strap, and setup the clutching. I set all of the KYB's to nominal for a good starting spot for shock tuning. First off, I thought the color was sick and looked insane on the snow. But it was a pain in the rear to keep the sled clean...it showed everything from exhaust soot to brake dust. I also wasn't impressed with the shocks. I played with the rebound and compression a few times and I could never get them stiff enough. I am an average sized guy...around 170lbs. They definitely could've used a revalve. The 146 was a pure wheelie machine as I was using the "boondocking" position on the limiter straps. I had the ski stance on the narrow setting (38") and found that the combination of the wider front end and wide running boards caused the sled to hang up on sidehills and took some effort to maintain the sidehill. I ended up totaling the sled from a rock impact.
I decided to pick up a 2015 154 Summit SP the second time around. I was able to save quite a bit and it left some cash for me to play around with. I ended up installing fox float 3's up front with the expectation to upgrade to the evol chamber when I'm due for a rebuild, fox float 3 front track shock, and the kyb pro 40 rear track shock. I also installed grip n rip braces (which btw have saved my summit more than a few times from tree impacts), rsi risers and freeride bars, rail braces, and clutching. Running the fox float's at 68psi, rear torsion spring at 3, and the rear KYB compression clicker 3 clicks stiff from the nominal position; the sled eats the big bumps and landings much better than the Freeride did. The ski stance at 36" and narrow running boards make sidehilling effortless, and the black colorway allows endless options for wraps. I am much more impressed with the summit setup this way over the Freeride. It's just works better for the type of riding I do...ripping the trail hard on the way in, and then pulling sketchy lines through the trees and jumping natural features.
Hope my experiences help you out!