Power, I guess. I'm not really that fussed about having the most powerful hardware or the highest resolutions or whatever, that's why I've only upgraded my PC once in the 7 years I've had it (because my old graphics card literally couldn't run newer games, rather than to make games look better) and why I've no interest whatsoever in the PS4 Pro or Xbox One X.
Portability means less than nothing to me though so power still wins. Portability is actually a negative as far as I'm concerned. I much prefer gaming on a proper TV or monitor with an actual controller in my hands (or mouse and keyboard for select games, controller is better for the vast majority though) and portables don't allow either of those things. People will probably say "but the Switch..." and yeah ok, maybe portability is a non-factor rather than a negative in that case, but that doesn't change anything for the Vita, the 3DS or even mobiles and it's still very much a negative for me on those.