FWIW, all line-in is on an R4 is a 20db pad. Same thing for a 660's XLR inputs, you can turn on the 20db pad or not.
Regarding the mic vs. non-mic pad, again I go back to my example. The choice for most of us is between a 10db pad on the mic or a 20db pad on our recorder plus gain. I'm sure it matters which mics and which recorder specifically, but the point I'm making is you can't just say "on mic pads change s/n" without considering the fact that you're alternative is a bigger pad and added gain, which also might affect s/n too possibly?
Anyway, I was just trying to rebut the whole R4 is useless thing. I think people bash the R4 way more than is needed really, but to each his own. Personally, I wish it was a bit more transparent and open sounding than it is, but then again, I can't tell you how many times having an extra spot mic or two, or an extra stereo pair, has made a HUGE difference in the recordings I've made. So, that's the tradeoff really.
I'm still trying to remember why Doug said something about liking a modded R4 more than the mods he does on the Pro. But I'm going to ask him again, cause I bet the same will hold true for the R44 (assuming he can even mod it).
Lastly, pretty much every recording on my website (see sig) that was made in the past year was on a stock R4, so if anyone wants any samples, there are a bunch on my website. Some of those recordings are only one pair, some are with two pairs, and many are with a pair plus a spot mic or two (I often run XY or DIN onstage and pull a direct from the bass amp cause I never seem to have enough bass in my ambient, and because in jazz, when the bassist solos, he's always too quiet, but in post I can use automation and raise up the bass solos, among other tricks, heh.)