If you are considering using a hi-lift jack, get someone experienced in off-road recovery to teach you how to use it. These things are dangerous if not handled correctly, but in the hands of a competent person they're supposed to be brilliant.
As the others have said, the exhaust jack makes for an easier lift in soft stuff. The big issue with the exhaust jack is getting the thing underneath - if you've dropped yourself into the mud/sand up to the chassis, you're in trouble. You need to be able to get this thing under the vehicle AND you need to connect it to the exhaust. If you're in really deep you'll be wondering where the hi-lift is.
Depends what you're doing. If you are doing a lot of off-road adventuring, you might find it better in the long run to get a hi-lift, have someone show you how to use it (both the right way, and the wrong way, and tell you why) and take it - plus some means of placing it on a loose surface - when you go.
If you're seriously considering a hi-lift, consider some steel bar-work front and rear with jacking points installed, and also get those wheel hooks as well.