Matt, my solution has been two antennas: both of mine are Comets, for no other reason than everyone else seemed to be buying them. I've got a longer SBB5 that is great for highway travel, on the way to runs, etc., and Moab. Then I've got the shorter SBB1 for wheeling in trees. Since my mount is up at the top of the hatch now, even the little one (think it's 18"?) gets bent over by trees, but it works very well for trail communication, and can still hit the repeaters.
But the longer one is better, no doubt about it.. proven several times this past summer on the Ghost Town & Ouray runs, as well as many monday nights talking to guys on the repeaters and on simplex. If you get a 7800 and a SBB5 antenna I'd be able to talk to you from your house to mine, but if one of us had a shorter antenna that would be more difficult, and impossible if we both had a short one. Not that ability to talk to me at my house should be any decision criteria for antenna purchase, just sayin...
Also I went to HRO and asked for a 2m only antenna, but they said you can't really get one, pretty much everything off the shelf is dual band these days.
82 fj40, 99 uzj100, 06 gx470
97 DR650, 05 525EXC, 01 XT225, 09 TTR125, 07 TTR90, 07 CRF50