I think The legion figures look great and the scale difference is very slight and in my opinion not a huge barrier to compatibility. but from what I have seen the figures are different stylistically.
IA figures are modeled in a true scale. Luke has proper proportions. This makes the figures difficult to paint but a very accurate representations of the subject.
legion figures are modeled to be easier to paint. Luke's head is larger compared to his body. The details are sculpted with greater depth then they would normally have as a true scale model.
The legion figure in this photo looks WAY better. mostly because the painter has gotten way better at painting since the first luke came out. That said most everyone will have much more fun painting the legion luke.
Also the legion figures at gencon were likely resin casts of 3D prints (look at the layers in Luke's base) i have no idea what the final models will be made from or if they will be as crisp and free of flashing as the legion figure. my rune wars figures have plenty of flashing.
I measured a royal guard and they were about 35 MM tall and I think that is a pretty good match for the Legion scale. luke just appears to have grown a few MM from ANH to ESB.
Also pictured is the imperial army I happen to have just sitting around getting dusty. lots of stuff here I could use in Legion if FFG allows it. if FFG does not allow it I will simply not play Legion and that is ok with me. if you were wondering just how much of an Imperial assault army would be useable in Legion this is my personal stash. I'm sure rebel skirmish players would have a comparable rebel army.
Note the base unit size for storm troopers in legion is 4 figures so a base box is actually two units +1 spare, toss in the storm troopers unit expansion and you would have 3 base units. I could see the heavy troopers being weapon upgrades or their own unit. imperial commanders could be unit upgrades, imperial guard could be a unit or they could be a body guard upgrade for a commander,
Edited by TylerTT