There is no BEST mag mount. In fact, they are dangerous in the event of a crash. This past February a bystander was struck and killed by a mag mount antenna which dislodged due to a crash.
I'm not too sure Wilson makes the best CB antenna because their literature exaggerate the facts. One of the most popular VHF/UHF amateur antennas is the dual band Larsen NMO270.
If you're looking for a monobander, a standard old quarter wave is hard to beat in an urban setting.
Roof mounting is preferred, with the middle of the trunk is second best.