Not to argue at all, but I’ll present a counterpoint based on my experience:
Learning DCS itself (as a sim/software) probably is easier in pancake mode. You can see the keyboard, so you don’t need an extensive HOTAS with everything mapped, and can refer to guides on an phone or tablet much more easily.
That said, learning to fly/operate an aircraft module in DCS is easier in VR, in my opinion. For one, the cockpit geometry is intuitive; you can move your head to see around the control stick, find switches and buttons faster and more easily and secondly, you have depth perception and a sense of feel for the aircraft that just isn’t present on flatscreen.
When using a mouse or hat switch to move your POV (look around), it adds an additional layer of complexity because not only are you flying the aircraft, you’re driving your pilots head, and you have to think about where you’re looking and how to achieve the view you want. Some cockpit switches are simply inaccessible without 6 DoF that VR can give you. I know that TrackIR is great too (used it for years before the VR evangelists converted me 
), but it has pitfalls as well, and can’t give you 1:1 head movement all the way around (clever curves and profiles can help there though). With VR, it’s simply something you don’t think about, you just do. Just like in RL, which makes it so incredible for me.
I too had ‘lack-of-motion’ discomfort (albeit very manageable and ignorable in my own case) early on in VR. Doing normal visual maneuvers, VMC-IMC and IMC never bothered me at all because as a pilot, I’m already adept at ‘turning off’ or ignoring my lying inner ear on a daily basis. What did get me the first few times was doing acro in VMC, like a loop; My brain knew what it should feel like IRL, and when it didn’t, pulling over the top my inner ear freaked out a bit. It was actually amazing to me, because it meant that my brain had fully ‘bought into’ the VR visuals up until that point. After a few times early on, I haven’t had that problem since, so I think that it’s possible for some people to power-through, much like IFR training. For some people, obviously not, and that’s okay; doesn’t make anyone a poor pilot or anything*, it just means the visuals are convincing enough to fool the brain.
The first few years I went to Level-D Sim training, I experienced motion discomfort while taxiing, since my brain knew what that should feel like, and when we made a turn, the sim couldn’t fully replicate that feeling (and understandably, probably not a great deal of effort is spent on the ground handling motion, compared to when the sim is in the air). Eventually I learned to stare straight ahead and keep telling my brain it was fake, until we got lined up on the runway. These days, it barely bothers me and actually strikes me as funny that it still does that a bit.
*One of the sharpest stick & rudder aviators I’ve flown with has been flying for 40+ years, and cannot do acro. He pukes after a few spin rotations or a gentleman’s roll. Always has, always will. IMC never bothered him, but he can’t handle acro, at least as a passenger. Says it’s the same way on roller coasters; go figure.
<<< In case anyone from E.D. is reading this, I’m not alone here.