I think it depends on your scoring system. If you get one point per reception and one point for every ten yards, I would start Garner. He is likely to have as many receptions as Holt (7 to 8 ), but he will probably end up with more total yards.
Garner is almost always a lock to put up over 100 total yards and on a good week can put up around 160 to 200 total yards. Holt would have to have a "great" week to match Garner's "good" week.
In addition, there is less downside risk with Garner. Garner will get you 4-5 catches and 80 - 100 total yards on a "bad" week while Holt will have a few games every year where he only gives you 3 catches for 60 yards.