I have checked out a couple. Because of the V shape, head room at the front of the bed is better than the rear. However, the bed is narrower. If it were 2 adults and 2 kids, kids definitely go up there. The lower bed is bigger than the SMB 50 bed by about 6".
You can easily find nice traverses around $20-25k leaving lots of budget for 4x4 conversion. The last nice 50 I saw sell was 2wd with 100k miles on the SMB website and sold for $35k.
With the 50 layout, there is less benefit to the full SMB pop top because you only stand in the middle of the van. SMB for sure feels roomier, but if you aren't living in it, I would rather save the money.