What I've noticed with vectors, is if you fully repair/verify the pieces; they'll generally run fine. That is, start at power, fully test, repair, move to board/monitor, do the same. Verify connections are good and everything should be good. Yes, they can be a bit more temperamental than tasters, but I've had worse luck with pole position than any cine/vb vectors. Also, my "chart" for the reliability of vectors tends to go as follows:
Atari b/w > atari color > segas > cine/vb
Ranging from easiest/reliable to least. It's also a toss up on Sega Vs cine/vb. They very well could (and probably should) be switched.