I enjoy, and use BOTH sites regularly, I have found many threads on both sites invaluable, It would be a shame to see any go away.
that being said, and being a semi-active user, I would say do what works best for you. clearly we all know about both forums so bouncing from one to the other would be no big deal, just the work involved if it is decided to transfer all existing posts by copy/paste method.
If the option were given to help in the task....I would volunteer a little time to help the cause.
this site flows better and it set up better than the EF.com but you already said that's the ONE thing you really want to change about it. so I say GREAT! make the changes, and I'm sure some of us will help carry over the posts.
will it take a lot of time and patience from users? sure.
will it be SOOOOOO much better in the long run to have ALL the info amassed in one easy to find, easy to navigate web address? sure.
in the mean time will it suck and be confusing to most? sure.