Tape. Those shields just don't work and they're fiddly to hold.
Discussion
I’ve been tape until today. The shield took some getting used to. It’s fast!
I suppose it depends how much you have to do. If you have a lot to paint in one colour and you can learn the physical skill of welding the shield quickly that's worth the effort.
If you're an occasional painter or you have several colours or tight corners, or even small rooms, then I think tape is easier for most of us.
I guess it really depends on your dexterity. If it's good use a shield. If it's average or lower use tape.
I love using tape it’s easy and consistent. But I’ve got a few long runs on ceilings so trying the blade/shield thing. It’s all about the right method for the need.