I'm not really comfortable with G1, so preferably Prime. The Prime storyline is easy to understand and pick up where it left off.

As to canon chars, I'm not really comfortable, since you're kinda confined by their original backstory and they don't allow for much character development. I'd rather prefer to come up with original ones.

[b]EDIT:[/b] I'll start the OOC once 5 people are interested. Invite your mates!