I own the VO frame you mentioned, but only have been riding it a month or so. It's a good bike, maybe even a great bike, but it's no Riv.
Before I knew about the Clem, I convinced myself I couldn't afford a Riv, and bought the VO on sale in December and then built it up over the last few months as I found deals on new & used parts. Then just as I was finishing the build, I had a chance to test ride a Sam, and man I think I should've saved up for that bike instead! I haven't ridden a Clem, so can't honestly compare it with the Campeur, but have to assume it still has that "Riv feel" that we hear about on this group.
I have the VO set up with drop bars, after mostly riding an old Trek TX500 bike w/ Albatross bars. I have the drops raised up quite high with a technomic stem, but it still feels like a big reach.... maybe that's just because I'm used to the upright bars, but I didn't feel that way on a Sam with drops.
I think the Clem has the VO beat on aesthetics, hands down. Better looking fork, lugs, colors, nice looking swoop on the seat stays, just more handsome all around. Mine is the 63cm size and it's funny to me how it doesn't look like a tall frame... maybe that's good, but I think I'd rather see a taller headtube and a sloping top tube, which would help get the bars up too. I think a tall Riv (e.g. 62cm Sam) does this really well. Clem doesn't have that size option, so maybe not a fair comparison there.
All of that said, the VO is great at a lot of things: Carries a load, no probs with heelstrike on my panniers. All kinds of thought put into it about racks, fenders, wheel clearance, etc. It's worth mentioning that it is built for Canti brakes, which could be a deal-breaker for some. I think you could swap out for centerpulls up front, but the rear would be trickier.