Ricky, if I didn't already have iphone 4 and lifeproof case when sony announced experia z, I would buy one.
After using lifeproof for about 8 months now, I keep my iphone in the lifeproof case all the time and never take it out of the case, I can tell you that I never have the problem you described. No problem in hearing other people or be heard.
I don't know how if it can stand prolonged motorcycle vibration though, cause I keep my phone in my jacket pocket.
If I must buy a new phone to replace my current phone, I would buy another iphone and another lifeproof case, not because I'm a fanboy but because I have bought apps like informant, pocketmoney, tomtom,sky safari, motion x, etc, and simply don't want to purchase those apps again