Sounds like you've got a good handle on your needs and how much tractor you need to satisfy them. The
BX2200 will handle your needs, provided you don't try to get too far ahead of the tractor's realistic abilities when you are doing things outside of your regular activities. /w3tcompact/icons/wink.gif
Yes, of course the
B7500 is worth the extra money. But whether you will make frequent use of the extra power/performance the
B7500 has over the
BX2200 is what you need to decide... and if you can justify the extra cost to have that larger, more capable tractor. I don't think the difference will be very noticeable when doing the regular the tasks you describe, but in the long run you're going to put less stress (and possibly fewer hours) on the
B7500 to accomplish those, and have more ability to do larger tasks outside of you usual lawn mowing and driveway maintenance. Most of those larger tasks that come up within the
B7500's reach will also be within the
BX2200's reach, except the
BX2200 is probably going to have to take smaller bites, work harder, or take longer to accomplish the task. What those tasks might be... who knows. Things will come up though. They always do.
There is nothing wrong with either tractor, and I think either would fit your needs. Also as long as you can "swing it" financially, there is nothing wrong with buying the slightly larger tractor, as long as it doesn't negatively affect your regular duties because of size (probably not the case).
I would also consider the attachment availability and capability of the
BX2200. While manufacturers are offering lines of implements specifically designed for use with the BX-series (more as time goes on), the selection you're going to find for the
B7500 will in fact be larger. That's not to say that any implement you might want isn't already available for the
BX2200, but it is something to consider.
The first jump from small mower to compact (or subcompact) tractor is a big one, and the difference between what you have now, and what you will have, is going to be huge. But my bottom line feeling is that with 12 acres, you're going to find plenty to do, and having the extra capability the
B7500 has certainly isn't going to hurt! So the
B7500 would be my choice, finances permitting.