Back in the air force I underwent hypoxia training, mostly to recognize symptoms, at a slow depressurization rate. I remember it being not at all unpleasant. You were barely conscious of the changes acurring to your mental state.
I recently experienced a rapid decompression to 12900' cabin altitude. A cabin pressure controller failed, the backup switching circuit failed, and as a surprise the fail safe mode drove the outflow valves full open. Timely actions of my FO regaining manual control over the outflow caves saved us from an emergency descent.
What I didn't expect was how the rapid depressurization felt. You felt very ill throughout your whole body. I can only imagine a catastrophic pressurization loss would combine the two, leaving very limited functioning ability.
The BA windscreen event happened at 17000', closer to what I experienced, not nearly what FL380 would produce.