Never use one computer for two divers, the profile can't be close enough. If your computer is air integrated get a regulator with two high pressure ports and install a backup gauge, then when the battery dies in 100 feet of water you at least know how much air you have. If you do a lot of advanced repetitive deep dives think about two computers. If it's electronic and goes on or under the ocean it will break sooner or later, and if it forgets all of your previous repetitive dives it might put a damper on an otherwise fine dive vacation. There are a lot of fine units on the market so it pays to shop them carefully.
Price is a consideration but safety is priceless.
Some are more conservative than others, and ascent rates vary. Ask your salesman, it's his job to know these things. Also ask about battery life and replacement procedure. Like any new technology we must adjust our habits accordingly. Unlimites, Inc., 1998-1999.