Hmmmm...
It would be handy to hear the conditions you are hoping to spear in and the type of fish that you are hoping to catch and the depth at which you are hoping to spear and....
Basically it is not as simple as following a binary tree for making decisions (in my humble novice opinion
).
Perhaps if you gave us more of an idea of what you hoped to acheive you would get a better answer.
I personally think that pneu's vs rubber is a bit of an open question as in different circumstances each has a pro and a con !
For example lets say that you hear that pneumatics are poor at accuracy and on that info decide to buy a rubber gun but the gun you buy is a long heavy aluminium one and you plan to use it in 3 foot visibility in surf or strong currents... it may be accurate as hell but you wont be catching many fish.
What is the visibility like where you are ?
in terms of propulsion I think that if you look at the videos on pescasub.com especially concentrating on the Mamba videos of Shane vs the wooden gun videos of some of the other ones there you will see that propulsion doent come into it too much in terms of those specific conditions and so on.
What I am saying is that you need to state all the details for the conditions.
If you want a long gun I think I am right in saying that you would be better with rubber as you can use multi bands for ease of loading - I am not sure how many people use 140cm pneu's ????
Personally I use a 100cm wooden gun with a single 19.5mm rubber band it is a totemsub pelagos with a rail and a 140cm 6.5mm shaft. I find it is good for aspetto and tracks well - I catch bass with it mainly here in Europe and it tracks well - I guess it has a range of 4m ? Maybe more - someone else will know.
Can you see what I use the gun for and at the end of the day it is just a tool to acheive an end - yes it is a bonus that I really like the gun and consider it an object of beauty in terms of the look and craftsmanship.
If you are interested in rubber then there are many different kinds of rubber too and you can change a guns characteristics by the choice of rubber and also the combination of rubber (single vs multi) and also lenght and thickness of rubber. So a tricky question.
It would be foolish to say that rubber guns are defintely better than pneumatic guns....
Well - if you tell us about the use and conditions you will suceed in finding out what you want - hope this helps !
Ed
Just noticed that you in the States in California - have a look at what locals use - also how tall are you ? Can you load a long gun or would you be more comfotable with a short one ? Find out and try to borrow some friends guns or ask as many people in shops that you can.
Alot of american guns are mid-handle - I have no experience of this....
Later amigo.