Tables used to be the standard. These days, most scuba divers use a wrist-mount computer and it makes sense.
A dive computer calculates depth, bottom time, ascent rate, and no-deco limits in real time. Tables give you a static plan. If you go shallower partway through, the computer recalculates. Tables are set before you get in.
Wrist-mount computers are what the majority of divers buy at this point. They're small enough, readable underwater, and you'll wear them as a regular watch too. best dive computers Hose-mounted models are still around but fewer buyers pick them anymore.
Entry-level computers run about $300-odd and cover everything the average diver requires. You get depth tracking, time, no-deco limits, a logbook, and usually a basic freediving mode. Mid-range gets you transmitter compatibility, improved readability, and additional mix options.
The one thing people don't think about is conservatism settings. Certain algorithms are tighter than others. A conservative computer results in reduced bottom time. Looser ones allow longer bottom time but at a thinner safety margin. It's not right or wrong. It's what you're comfortable with and your diving background.
Worth talking to people at a Cairns dive shop who uses various computers before you decide. Good dive stores will have a straight answer on what's good and what isn't hype. Decent dive shops have buying guides and honest reviews on their sites as well