Guess it would depend on what the seller means by resolution. Most people think it refers to CGA, EGA, VGA, etc. But some see resolution as how close individual phosphor dots (of the same color) are together, which can make one monitor look a tad clearer (with a smaller dot pitch). I remember buying VGA/SVGA monitors in the early 90's and trying to get the ones with a better (smaller number) dot pitch. I didn't notice a HUGE difference.
Maybe think of what you will use the monitors for. MAME cabinet, older original arcade pcb's, pc games, etc. If all of the above, you'd probably like a higher res, or multi-res capable monitor.
Maybe some real gurus can chime in. But I would think if you're installing them in a specific game, let's say a late 80's-early 90's arcade, you'd probably just like a standard resolution 15Khz monitor to match what they originally came with. A late 90's game, like Gauntlet Legends, you'd want a medium resolution 25Khz monitor. If you wanted to run it in a MAME cabinet to play some older arcade games on an emulator (say with an ArcadeVGA card), while also having the ability to play some pc games, you might want a 31Khz CRT monitor.
I'm no expert, so correct me if I have misled anyone here.