I had the same choice and decided on the garden tractor for the reasons you mentioned. That way I am not running up hours on my B3030 and I have the use of both. For example having the garden tractor pull a trailer that I load with the B3030. You can never have to many tractors

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There are a lot of quality used garden tractors in the 2-3k range.
I would look at the Ingersoll/Case tractors, JD or older Wheelhorse or Cubs. Some of them have 50 or 60 inch decks to. Check out the Lawn and Garden forum here on TBN -
http://www.tractorbynet.com/forums/lawn-garden/
If you have a lot of smooth finished lawn to cut and don't care about the tractor ability you can get a used commercial ZTR or a new homeowner version for around $3k to.