I have a VZ in both 7.62 and .223 and I've had a SU16... the VZ is SOOOOOOO much better. Only area the SU is superior is weight, but your trading so much for lighter weight (including longevity) its not worth it. Theres a reason most high quality, long lasting firearms are on the heavy side.
I would also like to say of the 3 VZ58's in .223 I've owned over the past 5 years, every one of them was FLAWLESS... in fact (ill probably get flack for this) I like how a .223 VZ58 shoots BETTER than an AR... It just feels smoother. hard to describe. With an $80 magwel installed you can run 50 beowulf mags and get 15 rounds in there (my VZ's ran the 50 beowulf mags no problem).
A VZ is a gun you buy and keep for a LONG time. An SU16 is a gun you buy, play with, then sell after a little while.