Note that Diamond advertises the gain of the NR22L to be 6.5 dBi (referenced to a theoretical isotropic radiator) which would be about 4.4 dBd (referenced to a dipole). You have to read antenna gain claims carefully.
That antenna is 8 feet long. It will require a very sturdy mount. I see you are anti-mag-mount, so that's good.
The NR22L is only available with a UHF mount. The UHF connector really was not intended to be a mobile antenna mounting connection. It is lacking strength compared to other antenna mounts, such as the NMO, and it is lacking in designed-in weather sealing. Yes, there are some band-aid solutions to keeping moisture and corrosion out of a UHF antenna mount, but they are band-aids, in my opinion.
The foldover mount on these antennas will require some attention. Over time, the spring which holds the antenna in the upright position will get weak. The result is antenna that is loose at the base. Also, the foldover mount is a place for corrosion to seep in which could make for a static-y signal.
Yes, the Diamond/Comet antenna designs, and the cheap copies of them, are popular and lots of hams use them. When I was first licensed, I thought they were hot stuff ( I used to have a Diamond SG7900). Nowadays, I use commercial LMR antennas, mostly from Larsen, on the ham bands. They are very reliable. A Larsen NMO150 is a 5/8 wave design with a real-world gain of 3 dBd.
