I'd go with a season pass. More potential.
As to area, hard to miss with either choice. Both great. Going early in the morning can make a big difference.
If you are big on mogul fields, then it is no contest: miles of em at Mary Jane; never crowded mogul slopes of all pitches are so much of the terrain (but on weekends crowded lift lines to them sometimes). I don't see that in your profile, however: so acres of mogul fields at Mary Jane might not mean much to you, as they don't any longer to me.
Loveland is less crowded, as mentioned, and it's upper lifts stay open in wind/snow storms more dependably than at MJ/WP. "Day of" and "day after" the big dump are tops at Loveland, usually. But sometimes good at Winter Park/Jane too.
I've noticed that on a powder day, at Mary Jane most of the first chair regulars tend to go for gladed, medium steep mogul fields first.
At Loveland, they go for a bigger variety: steep mogul slopes under chair one, but a strong contingent go to all sorts of other powder terrain, because it's good.
For reference, I get both the Rocky Mt. Pass and the Loveland pass most years (plus A Basin - for steeps, and the other stuff early and late).
Of just the two areas you are considering, on a powder/crud day and a day after, I'd choose Loveland. For other days more of a toss up, maybe Winter Park, currently.
For lift lines, weekend crowds and ease of driving, Loveland. For lots of variety and big size, Winter Park/MJ, although by less than some might think.
But overall, for me, Loveland, of the two, by a hair, given your profile and needs.
If you decide Winter Park, I strongly suggest the combo Rocky Mountain Pass (including Copper but not Steamboat - you already have longer resort trips taken care of). It is not that much more. If you go this route, then WP/Copper would have the edge over Loveland, by a hair or two. To me, Copper balances out the weaknesses of Winter Park. On its expert/advanced non-mogul slopes and lifts, Copper is often less crowded than Winter Park. It perhaps has slightly better, more dependable/accessable steeps and chutes (unless you are into uniform mogul fields). It has a lot of hidden, steep tree skiing that is really expert, almost nobody in there (but MJ/WP may have that too, don't know). The powder at Copper - and Loveland - lasts longer, over more and more varied terrain, generally, in my experience.
Good luck choosing. Nice problem to have.