Everybody likes gain, At least you'd think so by the number of Pacific Rim purchases. The truth lies elsewhere.
You get gain by compressing the pattern. The resulting pattern can be about anything depending on how, and where the antenna is mounted. But..... If your primary operation is via repeaters, your really don't want gain. Except that is, unity gain. In other words, zero gain! The reason is, most repeater sites are well above average terrain, while the mobiles operating through the repeater may be at any height. Therefore, what you really needs is for the transmitted energy to be, well, omnidirectional. That IS NOT a gain antenna in 99% of the cases.
Adding some insult, antenna placement is more important than gain. Here is an article (I didn't write it, but I store it on my site) for all those folks who think gain is the ultimate experience. http://www.k0bg.com/images/pdf/mobile_vhf_ant.pdf