Chrud, is the bow equipped with the same accessories as was your Switchback in terms of items which might affect noise? In comparing the two, are you shooting the same rest, limbsavers, string stop, etc?
I currently have an S2 and wonder about the difference.
The Z7 comes standard with a Dead End String Stop, Monkey Tails and a Harmonic Stabilizer. My Switchback doesn't have any of those, but it does have Limbsaver Ultra's on the limbs. The rests are different on the two bows. The only similarity is the stabilizer, which is a 6", 10 ounce Stealth on both. I'm not sure how much of a noise reduction there is from the DE, Monkey Tails or the HS. They all reduce vibration, which will result in a quieter shot. All three items can be purchased for a Switchback. The only one I would recommend is the Dead End though. My Z7, fully loaded, is noticeably lighter than my Switchback without a quiver.
I drew both bows side-by-side the other day and was surprised. The draw cycles are relatively similar. It is comparing apples to oranges though, as they are not the same let-off. The Z7 has a MUCH better balance than the Switchback. My SB, without a quiver (older style Arrow Web QD) is very top heavy. The top falls forward and to the right after the shot. The Z7 very well balance, with a little extra top weight. The biggest difference is the shot. The Z7 has a much more "dead" feeling on the release and is significantly quieter than my SB. The Z7 seems to have a harder wall also. And, the grip on the Z7 is much nicer than the SB.
In my opinion, there hasn't been a big enough positive difference in the Mathews bows since 2005 for me to upgrade my Switchback until the Z7 came out. I really liked the DXT, but there was only about an 8 FPS difference. The silencers the Z7 comes standard with can all be purchased for an S2/SB. It will be difficult for Mathews to top the Z7 (I know, we say that about every bow). It is, in my opinion, the total package.