MagSafe and USB-C charge the MacBook Air at the same speed.

Essentially the same. Apple’s MagSafe and USB-C ports on the same MacBook Air model both support the same maximum wattage (usually 67W or 70W on the M2 and newer, 35W on the M1). So if you plug in the same 67W adapter into either port, you get identical charging speeds.

The only real difference is convenience. MagSafe snaps on magnetically and won’t yank your laptop off the table if someone trips over the cord. USB-C is universal but easier to get disconnected accidentally. Neither one charges faster than the other.

I’d pick based on which cable you hate losing more.