Both C5 and C8 here.
Both will work fine. 5 has a simpler interface which I honestly prefer. My fav interface though was Nuendo 2’s interface. Super clean, slick…not cluttered. I’m old…LOL!
It’s a toss up. What kind of editing are you doing? what kind of plug in editing arranging do you need? And how often will you use the features in 8 that 5 doesn’t have?