Why people play the gain game is beyond me. Read VERY CAREFULLY what the gain figures are. With a few exceptions, most antenna manufacturers, especially import ones, over state the gain figures of their antennas. One of them gives gain figures based on a stock HT antenna (read that as a rubber ducky). Puts new meaning into the term dBd doesn't it?
Further, their gain figures are theoretical figures, not real life. Adding insult, the coils are small (read that as lossy), and the antenna as a whole is not very sturdy.
Remember too, in an urban setting, gain is not the most important factor. In fact, some lower gain antennas will out perform higher gain ones due to the take off angle.
If you want one of the finest dual band antennas available anywhere, look at the Larsen NMO2/70. Properly installed, it will last a life time.