TheBigPhillyFish :
About a year ago, I went through the same selection process of video camera / housing.
What I did was write down all of the features I wanted and debated the importance of each one. It changed over a couple of weeks until I eliminated all but one housing model.This is what I ended up with ::
*Budget - It changed and I ended up spending more than I originally planned
* Camera - HD no question,
tape vs HDD a couple of threads out on this. At the time the consensus was tape was better quality and easier editing. I was used to tape and it archives well
* white balance - became more important the more I learned, Glad I have it. Very good when it works. Made two dive trips with new housing ;the first it worked every time, knock on wood, the second trip it only worked one time, but when it works, it makes improved color
* Internal flip filter - CC filter is mandatory, if it is inside the housing it is always there when you need it, doesn't get lost during dive, is protected, and doesn't get bubbles Just make sure it can't come out of its holder.
*Travel consideration - I wanted something that breaks down, handles, ports, and two sections. Will fit into carry-on bag
*Warranty / service from reputable company
*Mechanical or Electronic control - I had electronic controls on my first housing, they failed the first trip without the housing flooding. All material will degrade over a period of time and this is one more thing to go wrong. the mechanical controls can be serviced regularly, and salt water will not ruin them, unlike electronics. Electronics are good as long as they are isolated from electrolytes, I am a little sensitive to this since I had a failure. Every dive, I didn't know whether it was going to fail or not
*Material - Aluminum; Hard Coated anodize, sealed, aluminum is machined to tight tolerances which makes the mating parts for seals very precise, aluminum is stiff which helps the seal groove remain stable and doesn't flex, finish is tough and scratch resistant, zinc corrosion protection. Alternative is painted surface on aluminum, or plastic. plastic doesn't corrode, but is not as strong or tough as aluminum. My old platic housing was susceptible to condensation when left in the sun. I still put a towel over my housing between dives, but is is not as bad as my old plastic housing
I will say I strongly considered an Ikelite plastic housing. The Lexan (OK its really polycarbonate; it's not a BushHog its a rotary grass cutter, on & on...) material is good, customer support is excellent. you get a lot for the money. Don't like the mirror
*Additions - Lights, monitor, leak detection, upgraded ports. maybe a tripood, carry handle, cases ( you can always buy a pelican or stormcase)
There are several good choices on the market, and they will all make good video. Some were not for me and I ended up spending a little more money and got a Sony HC9 and Gates housing. It is very robust, looks durable. I am happy with it. I usually keep equipment a long time so wanted something that will last and can be serviced. I know it is good for only one model camera, but I am OK with that. I am considering getting a backup camcorder at some point in time.
My new housing is small enough to pack, yet handles better than the barbie housings. It has all the functions I listed above.The main seal does not require silicon, but inspecting for cuts and debris is important. Right thumb controls start/stop recording while holding handle and left thumb controls zoom Everyone has their own desires. For me, a mirror viewfinder and electronics were the deal breakers. In fact, if that was all that was available, I probably would have gotten into photography instead.
After you get your underwater video, then the real work begins, it is important to have good equipment, but more important is buoyancy control and spotting subjects.
During a dive, I once watched this guy taking video a couple inches from a wall. He didn't move at all, without the finger-on-coral trick. After he finished he backed up (reverse frog kick) helicoptered 90 deg and continued down the wall. I wish I could have seen his video.
It is good to talk to the experts that sell these units. As mentioned earlier MarineVisions is also a good place. check the prices, they are usually same as B&H photo, plus you get support, advise, they stock equipment and you can get any accessories later.
If you are on a budget (who isn't) you might consider a flat port to start with and then add wide angle later, then you can go either way. In my opinion, the optics, especially for WA is more important with HD. I can say from experience that a wide angle attachment inside the housing is not acceptable. It vignettes and some cameras and housings won't accept them. Hopefully they are a thing of the past
I don't have editing equipment yet so I watch my raw footage on a HD tv. compared to what i used to have, it is a big improvement. Corners are well lit and sharp. Like being inside an aquarium. HD was my easiest decision.
Good luck in your decision
I wanna do the Cayman's sometime this year. Where did you stay at? I only get West Palm Beach next week, but its 8 days of diving. But I am still jealous.
The camcorder spends most of your time in the water on "standby", you see a great shot you flip it "on", then after the shot "off". On a typical 60 minute dive I might get 8-10 minutes of footage. On a day when I do 4 dives, I use 1 whole tape for the day, changing the tape at night, shooting some topside footage also each day. I have to change the battery before I have to change the tape! 
