Split pad all day, if you mainly play in handheld mode. IMO anything with a traditional joystick is better than those small joysticks, but I do miss clicky buttons on joycons.
But keep in mind that splitpad doesn't work in wireless mode (I don't think it even has a battery). Iirc there are some split pad clones that can connect via bluetooth, but I never used any of them so can't comment on that.
If you mainly play on TV, pick up a pro controller. Or if you are using cfw pick up a ds4 or xbox one controller, that's what I'm using right now.