Throwing my experiences out here...
As others have mentioned, the immersion in VR is truly impressive, even at lower resolutions. And the sense of depth and distance is absolutely a game changer. I used to have trouble with making smooth landings in FSX on a monitor, simply because I lacked any depth perception. Throw on a VR headset in MSFS or DCS, and I think I've crashed on landing only once, and that was because I stupidly locked up the brakes on my Viggen and wheelbarrowed it off the runway.
Downsides are definitely the performance hit, the lower resolution, and the limited time I can stay "under the hood".
At the end of the day, it's very subjective which is better.