if you decide to get a 510 mega, you don't need to get a mega atty....regular 510 stuff will work on it.
the egoT and the 510T (the
tank kits) use a different atty....it has a post to poke a hole in the
tank. I have not used one of those. I use a tank, but it doesn't require a special atty. the 510T is NOT the same as the 510 mega. here is a picture of the 510 mega and the 510 regular so you can see the size difference. I'm a big believer in having backups, so for me, just 2 batteries and a PCC would make me nervous (of course I always had several cartons of cigs in the house too)
most people here would recommend you get an ego for the battery life, as I said I have and like both, but I do use the joye510 the most.