The nitrox capable Shearwater has come up fast in price over the last few months - now basically $1070 US as opposed to about $700 US 4-5 months ago.
I was almost sold on the Nitek X until I actaully dove one and that was enough to convince me not to buy one ($1600 US). I won't go into details, but avoid it unless the price drops to $1000-$1200 as it is way over priced for what it does.
The VR3 is becoming old news but still commands $1300 for OC nitrox and $200 more for OC trimix. The VRX is new, but the $2K US price tag is pretty stiff.
The X1 is great - choice of software, easy to read, etc. But it has some downsides. It is expensive $1750 US plus another $175 US for the actual software), and it uses a non user replaceable (rechargeable, but not user replaceable) battery. I worry about things like that when the "company" is basically one person prone to stroeks, asccidents, retirements, divorce, etc that could spell doom for the "company" and leave you with a $2000 paperweight.
The Cochran EMC-20H used to be a decent deal at around $800ish for nitrox, and around $1400 fully loaded with OC/CC trimix and extra memory, but will now run $1700 before you add extra memory. And it had some odd gas switching issues making it less than stellar in caves. An X1 now makes more sense.
The Nitek Trio is a three gas nitrox computer and sells for $500. The Nitek Duo is a 2 gas version and sells for $350. Both make great bottom timers if you go trimix.
So... for $1100 you can get a Shearwater with trimix growth potential, still the best deal around even with the price increase, and a very capable computer with nice features. Or you can spend $500 on a Nitek Trio.
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Either way, if you dive deco (nitrox or trimix) with a computer, you still need a back up that may either be tables and bottom timer, or another identical computer. So add $300 or so for an Uwatec bottom timer or $350 for the Nitek Duo to use as a bottom timer.
In my opinion, a computer is not required for accellerated deco and/or trimix diving in open water, other than perhaps as a means to abort the dive quickly and significantly earlier than planned. The key skills that need to be learned in the Adv-N/Deco course are some in water skills, (holding deco stop depths plus or minus basically nothing, shooting a bag, gas switches, etc) but the academics are equally important in terms of deco and gas planning. In my opinion, computers don't bring much to the table in that regard and can create complacency that will eventually leave you riding a computer into a deco situation that you don't have the gas to complete.
It is fine to ride the computer - once you already have the primary, contingency and lost gas deco and gas plans completed and know what you will need for gas in the worst case scenarios. That will also give you enough knowledge to know if the computer is out to lunch and feeding you bad information. Those are skill and knowledge areas the course needs to teach you. And to be honest once you have done all the above, for all practical purposes, you dive the plan and the computer becomes the backup.
In a cave environment a computer adds flexibility in systems where you often have little control over the depth, and a computer is much more likely to take the primary role, but you still back it up with thorough deco and gas planning as well as an awareness of the limitations and increased conservatism that sawtooth and reverse profiles may demand.
In my full cave course the instructor wanted us to develop a deco plan for a particular dive. Upon completing it, I advised that this was the best way to do it (there were a few possible options), but that with the profile involved I would not execute the dive that way as there was no good way to address the deco issues given the profile and the dive could be better executed by another route. Once you are in the real world, you are the guy ultimately responsible for how you conduct your deco, so get real familiar with deco theories and the potential pitfalls involved (computer reliance can let a diver gloss over that facet of development as well.)
If an instructor insists on a 3 gas computer at the Adv-N/Deco level you have to ask why and you have to ask why he does not provide a rental if he really feels it is essential.
