I've taught this format since 1997 on all different indoor cycle bikes and I strongly suggest you stay with your first choice (Keiser M3). It has the most realistic feel and also comes with a computer. Additionally, since it uses electromagnetic resistance, you have fewer parts to break or corrode.
I only know one person who bought the TV version of the Spinner and they found it a little more cheaply made than the studio bikes. Maybe because they figure only one person would be riding it instead of multiple people during multiple classes?
I'm a little over 5' tall and I find no problem with the fit on the Keiser M3. Really, if you have a chance to try out different models, you'll definately feel the difference in the ride.
(No..I don't work for Keiser, I just really like the M3!)
Vertically challenged, but expanding my horizons.