[armitron]

Actually you lose quite a lot, which is of course everything that requires a graphical environment. Examples include smooth pixel-based scrolling (see my other reply below), extensive image support everywhere (e.g. EWW/elfeed/GNUS/Org) which includes animations, PDF viewing (native on macOS), true color / SRGB, SVG rendering, better font support including emojis on macOS and multiple frames.

Maybe you don't care about any of these but don't tell me you don't really lose anything.