A solid NMO mount will provide superior reception as compared to a mag-mount with the same antenna. It all really depends on the signal strength of what you want to monitor.
I've always had body mounts, usually NMO, on my vehicles - eventually. When the car is old enough that I stop worrying about the first ding - on goes the NMO! Before that I usually settle for a mag-mount or even a thru-the-glass antenna. I keep trying thru-the-glass and learn every time tha tthey are virtually worthless for anything other than very strong signals.
I suspect, but can't prove, that the NMO is better than the mag-mount because of the true ground that it provides.
I just got a new car recently. Started with a new Valor thru-the-glass antenna and switched the following day to a mag-mount with a "Hershey's Kiss" size mount. The thru-the-glass acted almost a a dummy-load! I was concerned at first about it staying in place because the magnet is so small. No problem, even in rain and at a speed that I won't publish. My interest is VHF high and UHF only. I don't know that I'd want to try a small magnet with an antenna tuned for the VHF low band.