Arguable. It leaves town at even number on the last day (i.e. 5v3) and so all 5 townies need to vote scum. After lynch they go to 4v3, and vig can save them if he picks right. I prefer vig shoots nights 1 and 2, so you don't end up in a 5v3 situation. (See MXXIII as an example why this is a bad idea)
Okay, Looking back through the games:
MXXIX (Dr Who): town has vig who shoots every night. Town wins. (There was lots of stuff going on here like vig and SK intersecting, no reveals of nightkill alignments, but ultimately vig shot, town won).
MXXVIII: weird extra night-lynch-kinda thing. Town used it to good effect later in the game.
MXXIV: vig shot every night, town won. (yes he tried to shoot town and was blocked...the point is that he did shoot, and it did NOT actually hurt town)
MXXIII: 2-shot vig shot night2-town lost.
MXIX: 1-shot vig existed, didn't shoot, town lost.
MXVIII: 1-shot day-vig. Shot town (Day4). Town lost.
MXVII: one-shot Vig shot mafia(N2), town won.
MXVI: looks like one-shot vig shot mafia(N3), town still lost.
MXV: vig died N0. town won.
MXIV: day-vig? didn't shoot, town lost.
MXII: vig shot hider target and died N1. Town eventually lost.
MIX: vig shot mafia/werewolf night1 (looks like?) shot town after that. SK eventually won.
MVIII: 2-shot vig shot IC night 3. This was widely regarded as a mistake. town lost.
MVI: one-shot weak vig killed mafia and was saved by doctor (N2). Town won.
MV: insane doctor (i.e. vig) shot mafia for the win. town won.
MIV: one-shot vig didn't shoot. town lost.
I dunno, I'm not seeing this crazy huge negative impact vigilantes have from shooting. Not shooting is just as bad.
If we eliminate the one-shots we have only games where the vig shot every night they were alive. In every one of these games, the vig shot Night1. (I think these are V, IX, XII, XXIV, XXIX. town won 3, SK won once, mafia won once.)
I think we probably need more data points...but here's how it works out so far (I'm logging the full-vigs that shot every night as night1, since they're the only ones that have done it):
Vig Shot: Night 1/Day 2 Night 2/Day 3 Night 3/Day 4 Didn't Shoot
Town Wins: 3 2 0 1
Scum Wins: 2 1 3 3
(Note: I didn't include MXXVIII. MXV I counted as vig didn't shoot, since he didn't have a chance.)