Do you think the FM909 is better or worse in that regard ?
I'd guess about the same, I don't have an FM909, but do ride a new rev Signal Peak with similar suspension layout. The SP is a 115mm true 4 bar though, so the 909 should actually pedal a touch better in open mode - not enough that I would notice probably. Most of the newer FS XC oriented bikes have a lot of anti squat in their suspension design.
For me they're all about the same, except the opposing mini-link (dw-link style) bikes. I like the mini-link suspension better for technical climbing, but they have been high maintenance - at least in my experiences.