It is pretty simple, the Tan Tien is basically the little bro to the Dervish. At just 39" (99cm) the Tan Tien is about 4 inches shorter than the Dervish.
But what does this actually mean? The shorter Tan Tien is going to feel more nimble and quick turning. It will also be a little lighter and easier to carry.
The cons are that the Tan Tien is not going to feel as stable and will be slightly harder to ride.
We recommend the Dervish for brand new riders looking to cruise or dance. We recommend the Tan Tien to riders that have ridden skateboards before and want something more maneuverable.