I vote
Wilson on the antenna...the higher you mount it, the better the signal (transmit and receive) will be. I also
STRONGLY agree with setting the SWR correctly...makes a world of difference when it comes to transmit/receive clarity as well as distance.
I started out with a magnet mount on the roof (Li'l Will), but eventually drilled a hole and mounted mine through the roof (Wilson 1000). The through-the-roof mount is removable,
[EDIT for clarity: the COIL is removable, the hole and mount remain - a cap is threaded in place of the coil] so it's not on all the time (garage clearance or just not needed/wanted).
I've carried a conversation with a person that was ~20 miles away with my Wilson 1000 setup while sitting in my driveway (he had an amp/footwarmer/heater on his setup). The driver said I was "loud and clear". Conversations on the highway were getting similar reports. Keep in mind that geography (mountains, hills, valleys, flatland) and weather (cloudy/rainy vs. sunny/clear) all play a part in CB range and clarity.