Flip Camera Question?

Which is better
Flip Mino HD or Flip Ultra HD??
Also
Flip Mino HD has a 4GM memory 60 min. of recording.
And
Flip Ultra HD has a 8GM memory 120 min. of recording.
If I get a Bigger memory Card would that increase the time of recording ??
http://www.theflip.com/products_flip_ultra_specs.II.shtml

The best one is the Flip Ultra HD, it records for [...]