There is only one way to dive the Red Sea - liveaboard - do not waste your time/money with any other alternative!! Basically, you will have the time of your life with a decent liveaboard operator. My recommendation would be Tony Backhurst (http://www.scuba.co.uk
) - they have been voted number 1 operator over a number of years and have an excellent range of boats (mostly only a few years old) - I have been with them over 5 times!
Your choice of itinerary depends on your experience - if you are relative novices then I would suggest a northern itinerary sailing from Sharm or Hurghada (wrecks and reefs is a good one and includes the Thistlegorm and Rosalie Muller WW2 wrecks - the former is a must see for any diver!!). If you are more experienced and want to see pristine reefs and sharks then I would aim a southern itinerary (brothers, simply the best, St Johns). These tend to be more demanding from a diving perspective (>50 dives at least) but you are guaranteed worldclass diving!! There is simply nothing better than waking up in the morning and jumping off the back of the boat for a quick dive before breakfast!!
Day boat diving from any of the major resorts is nolonger worth bothering with - most of the reefs that are in reach of day boats have been damaged and you will not get the same quality of coral, fish and certainly no sharks. That said, it is the red sea, and relative to most diving around the world, it is still overall very good!
Our last liveaboard trip to the brothers we were diving with thresher sharks and oceanic white tips - quite simply awesome!!
PM me if you need any further information - or contact Dan at Tony Backhurst - he will give you some honest info.
PS. Didn't want to imply that the north was for novices only as there are some great (and challenging) dives in the north. The Rosalie Muller is such a dive (40M) and not for a beginner!!