Headsets and ANR

I'm thinking about upgrading my Sigtronics S-20 headset. Right now, I'm
considering the Lightspeed QFR SOLOc and Lightspeed QFR XCc (with ANR).

I like the price of the passive headset and I also like that it has a
pretty high amount of muffling (28.7 db according to the selasfolk).

But, if the ANR headset really is worth the extra expense and hassle,
I'd rather get the right headset the first time.

I have several questions:
1. Has anyone here flown both models?
2. Do the numbers in the sales-literature mean anything in real life?
3. I know that the Decibel scale is logarithmic. Does the ANR noise
reduction reduce noise in such a way that I can compare headsets by
adding the passive and active ratings together -- or is the cumulative
affect that you hear when you turn on the headset require more subtle
math to calculate?

Thanks,
-Luke