I use a fourth hand tool all the time, and find it much faster than using a third hand and pliers on brakes. it's also handy for derailleurs that need a little extra tension for whatever reason, popping off cap ends and pulling crushed cables out of pinch bolts with little effort. only downside is that they don't work well on cables cut less than an inch or so.

i use a park at work, and bought a pedros (which is probably just a rebranded lifu) for home. there's a big difference, as reflected in the price. the park is more ergonomic, while the pedros fells chintzy and doesn't always release the cable crisply after you're done. but the pedros is adequate, and fourth hand tools are a bit of a luxury if you only occasionally work on a bike.