I have had both and I prefer the XL.
I am able to comfortably play the system at arms length which helps with eye strain. When I go back and play the original or my DS Lite it now feels weird holding a system closer to my face since I'm forced to look at smaller screens. If you were to play the XL as close to your face as the original 3DS then you will probably notice the resolution, but in my opinion the XL is meant to be played farther from your face (feels more like a console experience to be honest rather than a handheld experience which is a welcomed surprise for me).
Pros
-Better buttons (especially the L, R, start, select, and home buttons)/stick nub
-Bigger screens
-Better build quality
-Smooth matte finish rather than shiny, smudge attractant, sunlight glare gloss finish
-Better DS playback (original 3DS does not emulate DS games as nice, google it)
-Improved battery life
Cons
-Worse speakers than original 3DS
-Less portable than original