I don't know if it holds true for all vectors, but the really flat first runs are pigs. Domier vectors, in my experience weren't quite as LSS and were more prevelant in the second run.
This actually gets pretty complicated...The FR Vectors, especially the earlier ones, had quite a bit of variation. Considering MVP's discs have 2 parting lines (overmold and core), and PLH is more important than dome for determining stability, I haven't found "dome" rules to hold completely true with any runs of MVP discs. I threw a lot of different FR Vectors, and some of the domiest are most stable(green), yet other very dome ones are not(clear). I also have thrown flat FRs that are pigs at all but the highest speeds and never did get one of the straighter flat ones that many posters mentioned at the time.
Long story short, here's my basic experience with Vector runs:
FR--These have the most variation, especially early on. The most overstable Vectors come from this run, but obviously they are not all that way.
2nd(and perhaps 3rd?) run--These have very uniform moderate domes from the ones I've seen and fly straight with a late fade on a hard and flat throw. They tend to glide a bit better than FRs imo.
Eclipse--These came out flatter than the 2nd runs, yet fly very similar to them imo.