WWW,
So would you do UA PP in solid IMC deliberately? If you would then you obviously think you're a better pilot than you probably are and you're liable to be a danger to other people (I think Freud had a theory on personnalities like this). If you get into difficulty, say a spin, be it a 'student' mistake, an aircraft problem etc, then I'd say your chances of survival are much better if you can identify the problem by use of a visual reference and correct it straight away, rather then either relying on the turn coordinator / ASI or waiting till you pop out the bottom 1000' above the ground to sort it out.
In the 'old' days before gyroscopic instruments they used to do IMC let downs by placing the A/C into a spin above the cloud layer, spin through and recover once through. This is all very well assuming two things....1) you know which way you're spinning....and 2) you have enough altitude below the cloud to recover....neither were present in this case.
Rgds
EA