honestly my arguement has always been with the exception of really smooth (ie like literally nothing on the trail and not bumpy) trail that suspension is faster. Finn part of the twitchiness was also the geo of that bike which is alot quicker than your Ibis is.
I am not sure you can see this. but this a local loop in a larger trail system in Pittsburgh. its a 2.2 mile XC loop 90 percent singletrack. I know the trail very well and it short enough that I can sustain 100 percent effort all the ways though.
My fastest time is 12:31 on my Anthem X, my next 2 fastest times are on the Anthem X as well at 12:47 and 13:43. The 13:43 time I know I was not trying as hard but the 2 12 minutes times are basically 100 percent effort with out many mistake. Yesterday I got my hardtail back running I go up with the purpose of seeing what is faster in as controlled of enviroment as I can get. No mistakes and my time is 13:48. So basically flat out on my hardtail and I am slightly slower than cruising on my FS, and one minute slower than crushing it on the FS.
This trail is literally one of the easiest trails in the pittsburgh area. but there are ton of little bumps,roots, log crossing on dips that make it tough for the hardtail to put power down. My limiting factor in most trails is traction both during turns and putting power down. FS helps both of those help quite a bit.
crappy video of the trails on this little loop. Looks buff and mellow right? you would think a hardtail would be faster right?
so why do I still own a hardtail? because its different and its fun and generally my SS hardtail is alot more reliable than FS geared bike. It makes me faster but it is no means faster.