like i said to each his own. but not much faster? i gotta call bullsh*t on that one, my wifes renntech is superb and every one ive seen is always ideal. no long term testing, sure there is its called amg. fayhl was with amg for quite some time and his talents as a supertuner are legit. there is not an amg altered merc out there that is not equaled or surpassed by a renntech. there is no renntech equivelent to your amg s55, yet. ya know, this is like when slp engineering was doing their thing, and doing it well, then the overlords and yuppies at GM decide to do it also cause they see how well slp was doing, so voila you got (ooops, you had) the return of the ws6 trans am, yet it was never but a wannabe of the firehawk. amg is good, i do not contest that, but renntech is at the least equal if not better (and as for cosmetic and aesthetic there is no comparisson). i do not know if you spend any time in europe, im there occasionally. check around and see who prefers what on the autobahn. like i said though this is obviously opinion either way and neither of us is right, as it is preference. bottom line, good luck with your benz.