I have a very simple animation that consists of two frames and two gif images. (front - back).

The example is here
http://www.wlmark.com/globe/

The top globe spins very smoothly while the lower one is some what choppy.

they are both set to
260 tweens and speed of 16 fps.

When I did the top globe, 260 was the magic number or else it looked choppy.

For the lower globe I resized the continents in photoshop and then using the same movie I deleted the big continents, resized the movie and the globe Then inserted the smaller continents.

I have played with many combinations of fps and tweens and when I go to single step some times the top continent moves but the back one stays in the same place and some times vice versa. which may explain the chop.

Any advice, tips, solutions or comments are greatly appreciated.