You can't go wrong with any of the 3 options, but I personally wouldn't do the Noveske Lower/VLTOR Upper. I would match a Noveske upper and lower if I were going to do a Noveske build. This is solely a cosmetic opinion.
My 2 Mega Billet ambi builds are flawless, VERY tight when you receive them, but they "work" themselves in to be very functional yet perfectly tight enough to not have any looseness once you use the rifle.
My vote goes to Mega, just because I love the way they look. But a matched Noveske set I did consider when I was deciding on which billet set to get, and if you decide to go with one you won't regret it.
Basically depends on which one you like the look of most. If you want to spend about 50% more than a Mega Ambi set to get the Noveske set (price wasn't exactly a factor in my "no expense spared builds", but it may be something to consider). Noveske definitely has brand recognition, but then again, so does Mega - all I see on here are people saying that Mega receiver sets are very hard to beat for fit and finish.
Best of luck deciding. Like I said, either way your rifle will be beautiful.