Started with a Nova, now run a SN.
Most desirable difference for me was the ability to adjust cant and drop of the stock. Other than that both received: mag cutoff removal, front stock cut/modified for easier loading and to eliminate possible binding, removed textured lines from bolt release lever and rounded the ends, action arms and bolt surfaces smoothed and diamond honed, forcing cone lengthened, added mercury reducer, loading port mods, stippled stocks, limbsaver recoil pad and added flip up sights for slugs.
I've seen some have the action arms shortened for faster cycling but I've also witnessed those same action arms break in pieces during a match...