In general, can anyone recomend the best rowing machine features? I'm not really concerend with the type (water, air, piston, magnetic).....My main question is the difference between the machines with variable arm motions and single arm motions. Do the machines with variable arm motions provide more range of motion to focus different areas of the back, or is the difference in range of motion so slight that the benifits are negligible?

I'm also very tall, 6'5", has anyone ran into any problems with the machines being long enough?

Any comments or suggestions is appreciated.

thanks