Seems there's a lot of advice here from some seasoned experts. Always great to hear, and better yet heed, the advise of those more experienced than you are.
But let me give you another 'newbie's' take on your question. I've been certified less than a year, and the same question on getting a pony vs. spare air crossed my mind more than once as I started to get into getting my gear.
From my perspective, I was looking at a spare air vs. pony in the same line you are - extending my safety net. I know how to plan my dives, and I do every time - regardless of whether it's a training dive, a 'tour' dive where a divemaster is telling when to come up or a plain rec dive without instructor supervision. IMO it's just a good habit to do regardless if it's been done already or not. Practice makes perfect. But as a new diver I knew I sucked thru air (SAC rate of about 1.15 when I started). I felt while it's a piece of emergency gear, the more air the better - right?
Well I decided to hold off, and in no small part to the numerous discussions & comments here on the topic. Instead of rushing into one I held off a while to see what I'd really need after getting a bit of experience under my belt. I already owned my fins & mask, so I bought my BC, regulator, all accessories (lights, SMB, bags, etc.), computer and a backup computer.
Instead of spending the money on a pony bottle I spent the money getting more training & experience. Almost as soon as I finished my OW I got my AOW certification. OK, 5 more training dives. Next I added a couple specialties. PPB, was the first (well second after EAN) and a big plus in helping to get some better SAC rates (but still not great). I then went on vacation and was able to get 10 more instructor-led dives. By now I'd had about a dozen dives and thought I was ready for some vacation dives. But though they were vacation dives I still learned more information from the tours instructors who led the group on the dives. After I got home I completed the Rescue Diver course and the Deep diver specialty, along with a couple more specialties. On the deep dive class dives the instructor made me wear the pony for all the dives, just to get a feel of it. I know now it's not something I'd want to carry on every dive, it really affects your trim. But I got the chance to carry it, and use it for a simulated emergency deco stop for (pretending) to exceed the NDL's. After those I went on another trip and found something wonderful. Over those 5 dives my carried weight dropped from 18 to 8 lbs in the same gear / conditions and even better my SAC averaged .70. Not the best, but far better than the 1.15 I had just 15 dives earlier. :luxhello:
Now I know I'll eventually add a pony bottle. I want to do some deep wreck dives next spring, and feel the pony will be a 'required' piece of gear for those dives. But it won't be worn every dive I do, and I know I'll never use the pony in planning. It's the divers version of an ejection seat on a jet. Use it only if the only other option is you're going to die (OK, or get severely injured). But should the right - or wrong - events line up I'll have it for the dives that do have a higher risk of issue.
I guess my thoughts after all this rambling is:
- Most new divers will consider a spare air or pony as an extra safety net (I did/do) they should have as they'll think it's good to overcompensate on safety items.
- The experienced divers will be split on whether pony / SA's are a good or bad thing.
- New divers don't really need a pony or spare air as they shouldn't be putting themselves in the dive scenarios where it would be a possible need (dives with multiple high-risk scenarios).
- GET MORE TRAINING! A new diver should keep getting training as it'll go a long way in improving your diving, both skills & enjoyment.
- Get experience! Best way is thru training, but get more dives in where you can honestly evaluate your skills & improve them.
- The best way to manage your air is improve your consumption and plan conservative. I'd rather 'waste' a few hundred PSI's in the learning stages than find I wasn't conservative enough. Plan conservative until you know what you use in which situations.
I'm still a newbie - I know that. I've got almost 50 dives in the past year, and know I have a long way to go before I'm anywhere near an expert. But I also know I'm much more experienced & skilled compared to what I was on the first dive after my OW, or even after my AOW certification dives were done. I've come a long way in a few dozen extra training dives in improving my air, trim & skills. And I know I have a long way to go to improve them to the best they can be.
So my advise, from one newbie to another, is get some more training dives in, improve those skills you think are good now & you'll be floored at how much better you can get. For now forget the SA / pony, unless you're planning to do the 'higher risk' diving as part of your training (like deep or wrecks).
Now should you decide to buy a RAS, which should you get? While I have not bought a RAS yet (it is low on my priority list) after looking into how many different emergency scenarios will it perform in, when I do get one the pony seems to be the only solution for me. IMO the Spare Air just didn't have what I feel I'd need for an emergency air supply because an out of air assent isn't the only air 'emergency' you may find yourself in if you failed to plan properly. For example, if I need to perform an emergency safety stop because I failed to watch my time & exceeded my NDL time (especially on a deep dive), a SA probably isn't going to allow me to perform an 8 minute, let alone a 15 minute, emergency safety stop. A pony is almost certainly going to allow me, unless I really blundered the air at the bottom.
Again, just the opinion & thoughts of another newbie. Thanks to the veterans here for allowing me a moment of time to let the newbie ramble..
