Between the 2, pick the SA2. Unless you really want adjustable focus which kinda sucks.
There are things that makes the P100A2 better that the SA2. It mostly is down to efficiency and component used. P100A2 is more efficient (not much) and has better components (e.g. springs as opposed the the SA2's bent tabs).
Pick the ET if you can make the budget.
Pick the SA2 if you like variable brightness. (ET has only 2 modes, SA2 can ramp up and down)
I used to suggest the ET but now I recommend the SA2 over the P100. Get the SC2 if possible because it looks that much better and is way shorter. P100C2 also is recommended. =)
(Sorry, most 2xAA lights are just yuckily ugly. Both P100A2 and SA2 falls here)
SA2 has SMO as well, if I'm not mistaken. Also, the SA2's beam is nicer.
If the admin wants you to close it, you should. It is in their jurisdiction what is allowed and not. If we use their forum, then we must follow their rules. =)
It means it can be submerged up to a depth of [manufacturer specified]meters for [manufacturer specified]hours. It's about as vague as you can get unless the manufacturer actually specifies it (most don't). Just take it as it can be submerged in water. Just don't take it diving.
Erm.. This doesn't make sense.
P100A2's have always used the XP-E.
SA2's also use XP-E by the way. And the SA2 has a nicer beam (if I'm not mistaken) due to centered LEDs. P100's tend to be off center a lot.