Short ram will give better throttle responce. Not much but a fraction of a second faster than the CAI from when you push down on the pedal to the engine reacting. CAI is still faster than stock but shortram is faster than that. Shortram will also not have the benefit of pulling in cold air, but hot air.
CAI... I prefer this. Hydrolock, yes more of a potential problem than short ram, HOWEVER.... the chance of a hydrolock is very slim. Unless you are regularly traveling through a foot of water for more than 30 feet... then there's not much chance anything will happen.
Yea you might get a slightly higher moisture amount in your engine on a heavy rain day if the filter gets damp... but it won't cause any problems. If it's raining that heavy, you should slow down, which is less pull on the intake therefore almost elminating the chance of anything happening.
Yea the bypass valve will help if you like to submerge your car in water... but other than that it's going to defeat any gains from a CAI and make it pretty much pointless.
I would go with the AEM CAI, tested and proven. I have the AEM CAI and have driven just fine in many heavy rain storms. One of our heaviest amounts of rain on record this summer and I've had no problems with it. I've gone through big puddles and splashes and regularly drive 30+ mins in a heavy downpour on the highway at 75mph... I mean uh 55mph, yea and have had no problems. :goodjob: