Although this is an old thread and an old subject, I thought it worthy of another opinion.
Theoretically the best antenna is known as an isotopic antenna. Unfortunately it really doesn't exist. For a mobile, the best antenna is one that works best for your individual setup. The reason I said that is because everyone does do everything the same when it comes to setting up a mobile or a base system. There are so many different factors involved it's difficult to have a pat answer for this question. And that not even allowing for a WAG OR SWAG theory.
Having said all of that, I have found that the best all around mobile antenna is a 102" whip but it would be hard to mount and use a whip antenna on a big truck because of the height restrictions and potential SWR issues.
Holy crap , this thread is like asking what is your favorite color, one has to understand antenna basics and determine what do you expect the antenna to do. For everyday trucks Firesticks will work, unless you need a bit more frequency range. If you want a broader antenna you will go with a Davemade, Monkey Made or a Fatboy style wide coil 1" shaft. The bigger the transmitting element the wider the frequency curve when tuning. So if you tune a firestick on 20 the swr may start rising by channel 10 and 30 where as with a wider surface area radial instead of just a coiled wire the swr may not start changing until channel 1 and 40. I see a lot of antennas rated for insane amount of power 35,000, 50, 0000 etc. if you are using a stock cb the only performance you gain is maybe in band width. If you get to the point where you are running 35,000 watts you know what antenna to use. Now having said all that the best antenna for the money is a 102" whip then I would choose a 4' Firestick and if I was running power and needed the bandwidth and power handling I choose one of the big coil antennas. Some of the other variables are the radiation pattern exhibited by the antenna due to its mounted location, for example an antenna mounted on the drivers side mirror will mostly reflect on the drivers side of the vehicle. If you have co-phased antennas one of each side of the cab you radiate in a type of figure 8 pattern. If you tune an antenna over asphalt the radiation and impedance of the antenna will change as you operate over different ground surfaces. There is so much more to this to select the proper antenna, but the best antenna is one that is properly tuned, not shorter than 4' and not broken Almost forgot, then we have base loaded and center loaded antennas like the K40's and Wilson's.
unless anybody can recommend an 81 inch antenna capable of handling a couple thousand watts and made out of copper like mine with a higher signal-to-noise ratio than stainless steel I think I will have to stick with my homemade antenna
Most are Clueless as to what a Good antenna is..
Just as funny are those using various sized pill boxes with Crappy radios & or antennas..
If one Enjoys CB and wants to get out..
Then get a Really good radio...
(ive never needed a pill box..besides most are dirtying up the signal..lol)
Get a good power mile (especially if using SSB)
Get good high quality coax (the crap 99% of people use..lol)
Then get a high quality antenna..
Back in 70's & 80's Hustlers rulled... Now its Predator
(unless using a Fully banded HF gear...then you need a high quality screw driver antenna)
But there is No Fabled one answer..
So deside on radio type
I perfer Icoms..though huge over kill for cb..lol.
Then use shortest but high end coax (makes a huge difference)
Then experiment with antennas and where-how to mount it..
I have run Monkey Made for years. There is not one better than the other, boils down to personal preference. As to running one or two antennas. I run two to equal out the look, but have only one hooked up to radio. Price, radio (whether CB, 10 meter, or 11 meter) can also be determining factor in antenna needs. I run a General Lee in my truck with Monkey Made antenna's. I have used the Wilson 500, and it was a good antenna also.