I have a B with a BH, it can do a heck of a lot of work. Here is a thread where I posted some BH pictures around a project I did with my B:
http://www.tractorbynet.com/forums/projects/291945-electrical-trenching.html I think its a lot more capable than a BX because its quite a bit bigger and the ground clearance is huge. I like it better than going bigger because it's a bit lighter (better in the lawn and not compacting the woods), a bit more stable on hills and there's a couple very tight places I need to fit in (driving through the woods and under a deck to stack wood). If you do a lot of ground engaging tasks the bigger and heavier tractor will help, for mowing and PTO then the cheaper and smaller B would be better.