Do you care to elaborate on the Video appears a bit degraded part ? I confess I didn't use advmame before, so I don't have a past reference, I just test it out on the Pi4 - the 3.9 version - to see how it works.
Overall, it looks like anti-aliasing doesn't work with the SDL driver. Examples:Vector game lines are not anti-aliased System menu font appears jagged Video Rgb Effects, such as scan2horz do not blend nicely with the game screen.
The setting display_antialias is set to yes, but there is no visual difference when it's disabled or enabled.
One of the draws of using AdvanceMAME is for the clean high-res Vector images, so that's a bit of a miss. But having AdvanceMAME available for rendering raster games like Cotton 2 and Baku Baku is a must-have.
There are also some issues going in and out of the settings menu (Tab). Sometimes, when returning to the game, the screen blanks. Also, gets very sluggish and occasionally hangs. Might not be related to the driver, but different from running this on a 3B+ without Buster.