All my SW minis are WotC too. And because Boba Fett is so ridiculously expensive in that range (in all iterations) by now, I opted to get the Imperial Assault one.
And there is a definite difference, even in that range. The IA minis are decidedly more heroic, but do not tower over the WotC ones.
The Legion minis however, are both heroically proportioned,
and scaled up, so those are indeed giants next to their WotC brethren.
Then again; when you take (relatively) scale neutral miniatures, like for instance Battledroids or Probedroids, they
can work alongside each other. So; no human(oid) miniatures, but larger ones like Banthas, Wookies, or some droids will work. Although no astromechs or protocol droids, as those dimensions are too well known.
I was way too late in picking up WotC Battledroids, and missed the time when they were dirt cheap. And now that I would like a few units as op-for, they're either impossible to get hold of, or ridiculously expensive.
So when I do get around to realizing that force, I will probably go the Legion route too, as for a Droid army, the size is much less of an issue (to my eye, at least). Unless of course I will have finally put in the time to get my resin printer working, and I print off an army's worth myself...