Think I'm ordering a Tobeco just to try, of 6 Kayfun full size clones, the Tobeco I have is the lowest quality, it was poorly machined, and I actually had to properly cut the juice channels because they didn't. I had 3 Tobecos ordered from FT, cancelled due to delays of nearly 3 weeks with no definite arrival time.
Twisted420's review, it appears to me the differences are very minimal. I do know everyone I've seen is happy with the Ivogo, and typically the Tobeco gets complaints, usually flow issues due to a smaller tank.
As for flooding, when you spin the top on as quickly as Twisted did, it is unavoidable, tighten the top slowly and you end up with minimal, or non-existent flooding, covering the air hole never seemed to make much difference on any of my Kayfuns. Inverting only helps if you leave the juice settle away from the flow channels. Fill it with a little care and you won't have issues.