In theory, the less a chain has to flex when bending around a chainring or cog, the slower it will wear. So if drivetrain wear is a prime concern, you'd want to use the largest chainring you can fit, and then size your cog accordingly to get the gearing you want. Since my fixed-gear is a converted MTB, I don't have as much clearance for a big chainring ~42mm away from the centerline as one would have on a track or road bike, so I make do with a 45T.