Steveky,
I have a T1670 and really like it. The only difference between the two is that the 1670 has slightly bigger rear tires and a rear suspension, which I really like. The deck attachment to the frame and the frame itself looks bulletproof. The hydro transmission is much larger and beefier than competing models from other manufacturers and is equipped with a cooling fan. The hydro is also foot operated, just like the big Kubotas.
To be fair, I don't have any other extensive experience with quality riding mowers to compare this one to. However, I have posted my experiences with this mower in previous threads in this section. Just do a search and you should find a bit of info.
If you have any specific questions, I'll sure try and answer them though.