Bustrewa,
The replies so far are pretty much on the money. I owned scuba first including 2 x 92 tanks. Once I bought a hooka I rarely used the tanks between their annual hydro tests.
For the 5-15m range, a hooka is perfect. Though I would not recommend it over tanks for penetration (loss of surface) wreck dives.
For deep dives (25m+) I would still use tanks, though I have used a hooka for 25m dives and been able to extend the dive longer than with tanks by doing the first part of the dive at 25m and then using the remainder of the dive (3 hours in total) working back up an essentially using this time as a deco stop. (With tanks available as a back-up deco stop supply).
A word of caution: if you go for a petrol powered unit, be absolutely sure that the air intake cannot fall down into the boat (where the fumes are). The filters will not take out carbon monoxide and you cannot taste/smell it. Carbon monoxide will kill you fairly quickly.
Happy (and safe) diving