I have two tri-sync arcade monitors and I've had no issues using them with mame. It's just a relay like what they use in many other household items. My central heating is constantly switching on and off via a relay and I have never had to change a relay in any house I have ever lived in.
It is not possible to make any accurate statements about how the image looks on tri-sync vs cga only monitors. A tri-sync chassis has no effect on things like scanlines when run in cga mode. They all look different.
Visible gaps between scanlines become more noticeable on monitors with less bloom. It doesn't matter if it's tri-sync or cga only. Some cga monitors have thick scanlines, others are barely noticeable. Same with tri-syncs.
As for the benefit of using a tri-sync, while there is not a huge number of EGA and VGA games, there are enough classics to make it worth thinking about. E.g. Daytona, Sega Ralley, Virtua Fighter, Ridge Racer, Time Crisis, all model 2 and model 3 games, Naomi games like Marvel Vs Capcom 2, Dreamcast games and older arcade classics like Paperboy and Narc, and newer arcade games like Street Fighter 4 and most PC based arcades.
So, for anyone that cares about correct native resolutions and refresh rates, a tri-sync is the best option. Plus, being able to run Windows in 480p makes it a lot easier to navigate. oh... and vertical games can be played at native res without turning the monitor (in 24khz).