action replay 4m vs saturn booster

i know they both do the same thing but are there any differences in the two? i also heard that you can't save directly to either of these cartriges, is this true? and if so how do i use it to save games?
with the carts, you have to save from internal memory to the backup cart, the only cart that I've heard that will let you save directly to the cart is the official sega ram cart.
but doesnt the action replay 4m have the switch also? and whats can i use the com port for?

(Edited by j3tt16 at 12:08 am on Feb. 7, 2002)