Which CMOS SPICE model should I choose?
The technology will determine the following things


Speed (smaller is faster)
Power consumption (smaller transistors consume less power)
Supply voltage (smaller transistors require a lower supply voltage)
And of course the required chip area


A 0.35um technology should be OK and you can work with 3.3V. If it is good enough depends on your requirements. In order to determine the speed you can achieve you can wire up a few simple gate structures and make a simulation.

A big advantage of 0.35um CMOS is that this technology is very cheap and protoyping is quite affordable.