gba had 3 of my favourite games (redfire, ff tactics advance, mario and luigi superstar saga) so ill go for that one! (ds was a revolution tho)

The DS was much better imo.
Better overall game library, and much better rpg selection.

DS.

It is a mixed bag for me.

I like the mountains of hidden gems on DS as far as creative game worlds, music, tone, art, etc. but I grew to loathe dual-screen gaming and touch-screen gaming by the end of 2007.

GBA had fewer gems, and I can only stand backlight screen/rechargeable GBA's nowadays a Modded OG GBA is more ergonomic, but I just owned a Backlit GBA SP.

But, I MUCH preferred the gameplay of a single screen with buttons, so I am more biased towards GBA.

PSP won me over in 2010 thanks to its library in the end.

Vita and 3DS was the same issues. I just wanted to play good games without touch-screen and dual-screen nonsense. 3DS had the games Vita had the right button layout (Vita even used way to much touch input and I went back to PSP in the end).

Android and iOS are prutrid dumpster fire.

I am much happier with how things are going with Nintendo Switch... I didn't buy Mario Party or Pokemon due to the motion control stuff, I felt complete with that stuff by the end of 2008 as well.