The miltek does droan, but only from new for the 1st 2000 miles or so. You will find this goes and my Non Res doesnt have any whatsoever @ 3500 rpm at high cruising speeds.
The Blueflame has ever so slightly larger outlets, sticks out the back a touch further then the Milltek.Has a slightly smaller,less large Rear silencer then the milltek, and is louder under hard throttle too.
Each person has different sound likings, so best bet is to find someone with it on their car and go try each.