Tables used to be the standard. Today, most scuba divers wear a personal dive computer and find here for good reason.
A dive computer tracks depth, bottom time, ascent rate, and NDL in real-time. Tables give you a static plan. If you go shallower mid-dive, the computer recalculates. Tables are set before you get in.
Wrist-mount computers are what most people use these days. They're compact, readable underwater, and you can wear them as a watch too. Console models are still around but not as many people choose them anymore.
Basic computers start around $250-400 and handle everything a recreational diver would need. You get depth, dive time, NDL, log function, and usually an entry-level freediving mode. The $500-800 range gets you transmitter compatibility, better readability, and extra gas modes.
The one thing people don't think about is conservatism settings. Certain computers are tighter than others. A cautious setting results in shorter NDL. Liberal settings extend bottom time but with less buffer. Neither is wrong. It's personal preference and experience level.
Check with people at a dive shop who's used various computers before you decide. Good dive stores will offer honest opinions on what's good and what isn't hype. Most good dive stores publish buying guides and rundowns online as well