floor jack is hydraulic. effortless lifting, and long enough to lift from the diff or crossmember
trolly jack uses springs. its basically the same jack you'll get in some heavy car, like a minivan or something, except its on wheels, has a longer pole, and is a bit heavier.
floor jack is not a bad investment if you work under your car a lot. saves a ton of time (takes ~20 seconds to lift & place jackstands) and your back, but it's not something most people have at home