I think the point about having a longer air hose is irrelevant. If you get a combined jump starter / compressor, then you'll be able to take it out and move it wherever you need it. On the other hand, if you decide to go with an industrial strength offroad-type air compressor, it will generally come with a much longer hose to stretch the length of the vehicle. So I think you just need to decide what you want out of your compressor - emergency / light offroading only, or heavy duty usage (air tools, lockers and the like).

If you decide to go the portable route, check out this thread:

Recommendations for a Battery Booster / Jump Starter?