In my opinion, anything new in that price range is going to be pretty much the same in terms of durability and reliability. These two factors are directly related to how you use and care for the rider. Dealer network for parts and service is nice.
About 6-8yrs ago, I would have recommended a Cub Cadet 2500 series rider. At the time a 2544 could be had new for $3K, was shaft driven, with an awesome serviceable hydrostatic drive. Today they are pretty much twice that price and have priced themselves out of the market IMO. For $6K, you'd be silly not to get a Deere.
I tend to have various spare equipment around, so downtime isn't an issue for me. I mail order most parts, so dealer network isn't a huge concern for me.