I looked at and tested both, ended up buying a different brand, but that is a very long story and the dealer, who I still do business with and from whom I have purchased 1 ZTR and 2 GTs from since that time, still regrets losing the sale. But he was on vacation and his guy screwed up!
The
B7610 is slighly larger, offers a nice advantage in the added horsepower while still giving you very light weight so it can be a nice all in one tractor without doing much damage to the lawn. (The tractor I bought is the same size, but heavier and does damage the lawn if I run over the same place several times). For a small property there really are a lot of good choices, Kubota has been growing and now has over 50% of the total small tractor sales in the US and in some areas is 60% of the sales. They make fine machines, no arguement.
Now the way I see it, every tractor is going to be a compramise to the buyer. The 7510 will be the worst of the small tractors of just about any brand I can think of for doing work like box blading. Not to say it can't do it, just saying there are better choices. But if you want to mow with little impact, then the
B7510 is a lightweight winner and is hard to compete with, let alone beat. The
B7610 is going to mow better if the grass is thicker because it has more power, it also has a more capable loader. But I don't know anyone who doesn't wish that they sometimes didn't have a bigger loader; 95% of the time whatever loader you have will make you very happy. On the other hand, the small light tractors fit better into stalls than bigger tractors. So again we are looking at trade offs. For 5.5 acres, either tractor would do well for you. I'd prefer (I always do) more power in a similar size package. For me, the future flexibility of running a larger implement that I might not even know I want, is worth the added price. My favorite tractors are fairly small but with the biggest possible engine within that frame size, I just think they are a better LONG TERM value because you can project SOME uses, but will always find others.