I definitely prefer a 720p screen because it's the best for scaling pixel art and retro games. If you have a 240p game (e.g. NES*, SNES*, Genesis*, arcade archives), it's a simple 3x scale, and everything lines up perfectly with the pixel grid of the screen. Shovel Knight and Sonic Mania look absolutely perfect on the portable screen, for example.
If the Switch had a 1080p screen, 240p content would need a 4.5x zoom, and nobody seems to implement that properly. Even watching Nintendo's own Super Mario Maker 2, I spotted some shimmering while the screen was scrolling due to the uneven pixel grid.
(*Yes I know about the 8x7 stretched to 4x3 thing, but even just having one axis correct is great.)