Let me give a shot at this. I will compare the 333skis, to the best of my ability, and ON3P too, since Rowen is with them.
From what I have seen, ON3P skis are amazing.. They are solid, lightweight, well built skis...
333skis, I do not know yet. I have a pair, they look and feel like they should hold up really well.
The boys at ON3P do a few things that I love alot. First, they use Bamboo. I have used bamboo skis and longboards, and they are just superior. They feel and respond better (IMHO), they are easier on the earth, and they hold up just as well if not better. ON3P also has a 3/4 wrap for the edges, and they have rubber dampening. I cannot say much for long term durability for ON3P as I have not owned a pair just ridden them. But I hear nothing but good things.
333skis are built on a comepletely custom basis. No other company can offer that, at the same price anyway. They have a similar if not better edge anchoring system than ON3P (kevlar anchor). But both companies use a 3/4 wrap edge, which is sweet. 333skis does not, however, use the all mighty ski press, or sidewalls. How much that affects long term durability and performance, I do not know, but people like sidewall and press built sticks better, so I guess it matters.
I am not too psyched on the nut for rivet setup, but I think it will be easy to just swap out rivets. Maybe Michael had a ton of nuts and bolts laying around? I dunno. But I think it makes them look cool? I dunno, I dont think I mind, but I might have to change it if I put my touring bindings on them, cuz I dont see putting skins over the bolts being easy.
As far as rivets, you should ask that over at TGR, they are more of a DIY crowd than NS.