I have the L3400DT (34.7hp with gears) -- great machine!
Light enough to not tear up your lawns (if reasonably dry), excellent power to weight ratio, very sturdy construction, tight transmission, super fast loader cycling, super cheap when compared to the competition in my area. Yes, it has a diff. lock and now comes with a hydrostatic (HST) transmission. At around 2600 lbs, it is not a feather-weight, but can really be loaded down with extra
ballast if necessary for heavy loader work -- tons of extra hp there to take the load.
I checked out the B series machines -- beauties, but they had more frills than I needed/felt like paying for. The competition couldn't match the price, financing, and service in my neck of the woods (JD, Kioti, MF).
Final decision came down to hp/$$. The L3400DT is a no nonsense working tractor -- plenty fun to drive, but you don't get cup-holders, etc.
Last thought: if you are a professional landscaper, you might want to give serious consideration to an hst model. Although I hate having to keep the rpm so high to get the performance from the hst, you will probably be running there anyways to get your jobs done as fast as possible. Split second direction changes, frequent loader work and changing mowing speeds would likely make this transmission more suited to your needs, too, I would think. Also, having employees grind the gears on your DT model might make you wish you had purchased the HST.
Sorry to talk so much, I just can't say how much I love this machine compared to all the others I have used "growing up on the farm".
Shawn
PS. Bob S. (and others) give some of the best advice you can find anywhere! Sure helped me.