I'm assuming by "safety" we are talking about minimizing the probability of being hit by a car at speed, as opposed to hitting a pothole or a curb or something...
I think suburban commuting *CAN* be safer than a busy downtown area if you can route yourself through subdivisions and parks where traffic is rare and at low speed.
If you're just straight-lining down a 70kph suburban arterial road with high-speed overtaking and cars pulling out at all other times... yeah, not optimal.