CFM says "3-5whp gain and a much more responsive throttle feel". I have heard nothing but good reviews on them. I cant say I have tried one because I have not.
As for the AEM CAI, get the bypass filter so "Hydro lock" chances are reduced to a minimum. If your engine fails to "Hydro lock", Honda's wont be on the menu.
Try out the K&N Typhoon, I love mine, it keeps the stock snorkel to bring in fresh cool air to feed the filter. The Typhoon also has a heat shield. K&N Says it is a CAI due to the fact that the snorkel brings fresh air to the filter and its by the fender. I would not go as far as saying its a "TRUE CAI" but it dose have a good design to keep cool air flowing to it.
2003 Sonic Blue SVT Focus #524