Rodales Scuba Diving Magazine analyses gear regularly. They just did a big spread on dive computers. You can go to your library or try looking on their home web page: http://www.scubadiving.com
You don't list where you are from. I'm sure there is a dive shop nearby. They should be able to answer your questions.
On a personal note: I don't like the wrist mounted computers. I like mine attached to the tank via a hose. What ever you buy, be sure it is something you can return in case it is not what he wants. Any good dive shop will do that as long as it has not been in the water.