the doctor V64 is a very good backup unit but it has 256m only
so yo can't play conkers bad fur day,resident evil(bio hazard),ogre battle,paper mario,pokemon 2 and 3 and some other.
and it's more difficult to handle saves.
The V64JR 512 can play all games,it's very simple to backup games and handle saves (thank's to obsidian tools) it load games faster than any backup unit.BUT YOU NEED A PC.
it has batteries to retain data
oh try this for tototek
http://www.tototek.com/main1/index_b.htm