I don't know if I have much to offer except anecdotal evidence.
I am 160-165 lbs. On mu IP-256SL, I have a 2014 RockShox SID XX G2 w/ remote lockout and 15mm thru-axle. Non-world cup. On my 2011 Giant Anthem X, I have a 2011 Fox F29 with the 15mm Thru-axle. I can feel no stiffness differences between the two of them. If anything, the Fox feels like it has a bit more play (despite a rebuilt about 150 miles ago), but it's also MUCH older and more used.
Both handle well enough for most all of the XC riding I do, even at speed. I wouldn't worry about the stiffness of the SID too much, though you are a bit heavier than I.
That said, I fell that the Fox is much more plush and tuneable than the SID. But I've only had the SID for a month and an still working on dialing it in. So far, I'm happy with it and with the lockout, but it isn't as plus as the Fox, plain and simple.
For the price I paid (a bit under $600 shipped for the SID BNIB), I wouldn't hesitate to recommend it. At the time all of the FOX forks I was looking at with remote lockout were $800+
I am really curious to try a Magura unit as I see them gaining popularity quickly.