Both matter. If you're going for wins, killing is a huge part of it. Map control is obviously what Domination is all about, and killing plays a huge part in that. By actively sending the opposition back to their spawn, delaying any attempt at advancement and flanking, you're also supporting the win by increasing the gap in score.

Every team needs a few slayers.

I play depending on how the enemy decide to play. For example earlier i was playing domination on Fallen and 4 out of the 6 players on the enemy team insisted on camping nowhere near any of the flags, so me and my team captured A & B and left them to sit in there corners gaining no score what so ever. But normally i just mix it up, constant movement around the map and trying to capture if possible

Grab 2 flags and spawn trap the enemy for kills. Get the win and the kills.

This idea needs to be taken with a grain of salt. It's much harder to win if you're watching killcams, however you have to have a drive to go for caps. There needs to be balance