I'll be honest I have never got wrapped around the handle about glass quality for hunting scopes. Binos and spotters certainly, as it makes sense to when I'm spending literally days a year behind them and picking out the animals. But for being able to put a critter I have already located in the crosshairs inside 1/2 of a mile I've found having uber glass quality is generally lost on me.
I've found just doesn't take top tier quality glass in the riflescope for the hunting I do. Again for binos and spotter I greatly appreciate great glass but its right down on the bottom in features of importance when it comes to riflescopes. Yes its nice to not look through a coke bottle but general I have found that if a riflescope checks all the other much more important boxes the glass has always been more than adequate for MY needs.
That said I find the 3-9 SWFA glass quite good and better than VX-2 and maybe on par with VX-3. Is it Nightforce ATACR good or even Bushnell LRHS? No, but its more than good enough. I cant think of a time when shooting a critter that the 3-9 SWFA would have been lacking optically and a scope with much better optics would have made it happen for me. But perhaps I'm lucky in that regard?
As far as eyebox goes the 3-9 def is larger and has more eye relief than the 2.5-10 ultralight. But the 3-9 is on a 5.25 pound 325 WSM and a 4.8 pound 338-06 (before optics on both) and I find that even without a break the eyelief is plenty good on those lightweight rifles.
Hope that helps.