rack just recently. While it worked just fine I like the roof rack better because:
1) it locks
2) doesn't get near as dirty from road grime(lots of small bugs end their lives on the bikes though)
3) it's easier to put the bikes on and take them off of the roof rack.
4) looks much cooler. ;-)
To avoid driving into the garage with them on I place an object just inside the garage door so that when I open it I have to get out and move it. It works.