Are you looking to buy the Cuboid Mini kit that comes with the tank or just the mod by itself?
Either way, I personally would use the Cuboid Mini as my primary and use the AIO as my backup.
I like Joyetech mods and have had very good luck with them. I don't have the Mini, but I do have the full size Cuboid and I use it quite frequently. It's a great mod. I also have the Joyetech VT, VTC Mini, and the Basic and love them all.
Without more info about your vaping style, preferences, and what you're hoping to do with the Cuboid Mini it's difficult to give an opinion either way.
If you post this question, with a little more info, in the regulated mods section of the forum you would probably receive more responses though.
Hope this is of some help to you.