Mugen has some post-Worlds revisions coming...
Losi is the lightest on its feet; but also slightly unforgiving.
The 8.5 is proven and has outstanding support via NitroHouse....but I'd wait on the 9...
The AE so far has been notoriously week and I question its overall capacity under club-style race tracks that are small/tight.
If I had to do anything right now; I'd go Losi (and I've been running a Jammin' for three years; so no bias in that dept.).