Ahh yes... That age old question is asked once again. Although I am perhaps not the best person to give counsel in this situation, I will try to to be as helpful as possible. Keep in mind that I am not a retailer, nor do I own/manage a dive shop at this time. However I have been there, done that.
Here is what I advise: If you are "just starting out" and have little or no experience with the various styles of equipment, then I recomment that you rent or try out the different styles and configurations "several times" before buying anything.
Many manfacturers stage events where you can actually "dive" their gear (DUI being just one of them). Many good dive shops will have a representative piece of gear from the various models that they sell, which they will either rent to you or allow you to try out. This is one of the many benefits of going to a dive shop rather than buying online.
Have a reasonably clear idea of the type of diving that you want to be doing and try/buy the gear that is most appropriate for that type of diving.
Above all else, the gear that you buy and use must fit you properly, must be comfortable on you, must function properly and should be appropriate for the type of diving that you are doing.
Additionally, you should always receive the proper training in the use and care of the equipment. This too is something that you can get at your local dive shop, and is generally not available online.
Whatever type of diving that you do and whatever gear you choose, be safe and have fun.
Seawolf sends