LOO!!! Been a long time dude!Having just got back from a pedalfest in Sedona and riding a Shova and my bro on an Imbuzi i would say the bigger and slacker Imbuzi.
We both ran 2 rings with DRS chainguide and lots of seatpost extension for the climbs. Throw in wide bars and flats and you sir will be ripping trail DH style.
He was hurting a little more on the climbs but i would think thats the price you gotta pay to have the confidence to go big on a trail bike.
The 2 frames are not far apart travel wise but based on your quote above you'll be happier with that little bit extra that the Imbuzi offers.
Remember too that the Imbuzi and some other trailbikes now have 1.5 steertubes so running slacker headset cups are possible if your looking to tweak the headangle.
Edit: That corsair trailbike pictured is pretty hawt.
I fully agree that giving these bikes a 1.5in HT is a great way to go. It just gives you SO many more options and greater strength in a shorter head-tube.