video resolution Defender and others

[jimmer]

I'm new to MAME, not using a frontend.
I run the games in a window (ie not fullscreen).

With Defender I notice 2 video options 4:3 and 21:17
and I note that 21:17 correpsonds to the original resolution of 294x238.

So which should I use to be most authentic?

I notice that in 4:3 mode my physical screen area is in ratio 4:3 (because that screen has square pixels?)

So if the actual game screen was physically 4:3  I seem to have the correct mode.

[Gray_Area]

If you're running the game in a window, why do you care?  Or, in further terms: unless you're runnin native on a CRT, and want to learn about all that underlines that, run it stock and just play some games.