Already gave my thoughts but just to add.
The standard all the way !!
It fits in back of a subie and rav-4. You can pile 2 in there if needed.
Buddy has a jr and its just that , another has an XL and the same deal.
I also have a shappell rover, it fits in back of above & a shappell 150 which don't . To me the standard jet sled is the " perfect " size ..
Another consideration is over loading a smaller sled which will make the drag worse then under loading the standard