If you do a "Build your own" on a comparably equipped BX vs a B, the difference looks to be in the $1000-2000 range. When you are talking about spending $20-25k, the difference is pretty small.Capacity comparisons here: https://www.orangetractortalks.com/forums/threads/bx-vs-b01-vs-b50.36719/
I moved from a BX to a B. In my opinion there are no downsides to that move - they're basically the same size machine (length, width are very close), but the extra height gives the B much better geometry on the 3ph. My opinion is that the BX is sized to look/feel like a large rideon, for people who aren't comfortable with a tractor, or who's wives can be convinced into a large rideon but not a tractor.
If you don't have that constraint, no reason to get a BX. The difference in price is not much, the difference in capability is substantial. A B will do anything a BX will do - it'll fit in the same spaces, turn as tight etc. But there's lots of things a B will do that a BX won't - particularly when it comes to ground clearance and lifting things on the 3ph. The extra lift capacity on a B is also really useful if you're getting a grapple - it's hard to get a lot done with a grapple on a BX because the SSQA + grapple on their own eat up a lot of your lift capacity. The B is only 30% more FEL lift, but once there's a grapple on the remaining lift capacity is more like 50%
If I were buying new or if I found a similarly equipped BX and B for only a 10% price difference I would go with the B.
With that said, I am very happy with my BX and it does everything I need it to. When I was looking for a used tractor I looked for both B's and BX's since they would both fit my bill. I got what I felt was a pretty good deal on my BX, so I took it and am happy.