As I am expecting to get a Kub 7610 delivered any day (week?) now, I have been reading these threads with great interest.
Given the negligible difference in weight between the BX and 7500, it seems to me that cutting capability is the biggest issue you have with the 7500.
Before selecting the 7610, I was concerned about the ground contact decks cutting ability compared to the BX's suspended deck. My neighbor has a BX, and his yard always looks fine, similar to my yard mowed with the 445.
I had my dealer bring a demonstration 7500 to my house. For an hour, I mowed with it on both finished lawn and a rough field. After it was taken away, I pulled out my JD 445 (60" suspended deck) and mowed.
For the field (thick grass), the 7500 was vastly superior. The JD just didn't have the HP to use the 60" deck in the thick grass. The 7500 didn't come close to bogging and gave results much better than the 445.
For the lawn, I can honestly say that you could not see a difference. My lawn is definitely not the smoothest. I usually use a roller in the spring to smash down the areas that get heaved upwards during the winter, but I have not done this yet this year. So....my lawn is bumpy. So bumpy that it is irritating, especially when trying to mow fast.
For me (3.5 acres), a BX could certainly accomplish everything that I want to do with a tractor. Initially, I just assumed that I would end up with a
BX2230. I test drove one, and remember thinking that it sure is not as comfortable as my JD 445 (even thought the 445 is much smaller). I am 6'-2" tall. I ended up looking at bigger JD's (much more comfortable than the BX), the 2210 and 4110.
Some of the local JD dealers really pushed the 2210 hard. others definitely advised against the 2210, saying that the entire design/construction process for the 2210 was greatly abbreviated and that the tractor was developed for the sole purpose of having good stats and pricing compared to the BX versus quality/longevity. This sounded legitimate, as the 2210 seems to share very little with its only slightly larger 4000 series cousins.
I was resigned to paying a lot more for a JD 4110 when I realized that surely Kubota must have larger tractors that are more comfortable than the BX. I drove to a dealer, found the 7510 and ended up buying the 7610.
I'm sure you will take a beating trading the 7500 for a BX. Make sure you find the BX to be comfortable. If it is acceptable, I guess the question is whether the possible improvement in cutting capability (get a demo and see for yourself if it is better) and grass wear (maybe you can increase the radius around obstacles to reduce wear) is worth the loss. My gut feeling is no.