Thanks for all the recommendations on different radios, I do appreciate it. I've been kinda wondering which are better than others and which may have some features that mine just isn't capable of. I may eventually replace the radio, but I'm in no rush - for my specific case of wanting something small in the jeep with limited space, I like the idea of the controls on the mic... the lack of "no PL on RX" is an issue, but not too big of an issue just yet. Since I don't [yet] have access to any local repeaters it's not a big issue... hopefully one day I can find some repeaters, then I could see it being an issue, and then may swap out the radio. So I'll take my time and research the radios now, so if/when the time comes I'll have a better idea of what I'm looking for. For a long time I was thinking to move away from CB to GMRS or HAM, but didn't really compare different radios - and didn't know enough about them or the technology. Going with the Midland micromobile was somewhat of a hastly decision I made, but while I am learning more and more of what it's missing, so far I don't entirely regret it.
I'll keep an eye on that other thread as well... thanks again to everyone for all the advice!
As for my original topic of antenna performance, for now i'm happy with the no-ground plane antenna that I have. Eventually (time-permitting) I'll add another NMO mount to the top of the tire carrier, and will compare the performance and post the results.