Did anybody ever answer your question? I'm looking at the same thing: a 2011 FE 390 vs. a 2010 FX450. The FX is about $1000 less. Really leaning toward the less expensive bike but I don't know if there are any significant differences.
FX has a 5speed close ration gearbox and CC forks The FE are 6Speed wide ration gear box 2010 has OC forks 2011 has CC forks and some added welding to the frame to stiffen it up FX usualy come with a race kit too I think but not sure if they are still doing that
On the FX model they came with a race kit it had a FMF exhaust and a voucher for fork re-valving I think that was it about 1500$ worth of stuff I'm pretty sure they don't do that now though