I was just talking about the RWRP middle with some guys on another forum. What is it you lose when you do this exactly? Top end?
I actually must spend some time pondering on what exactly it is that is lost with the hum, as it is hard to say and even harder to put into words.
There is the BKP tutorial you can find here
http://www.youtube.com/watch?v=j2Z7ZIKAXTA which shows it off rather well.
I will not attempt to describe the difference at this rather late hour (at least for me), but rather just point you to the video. I have two HSH sets, one with a RWRP middle and one stock (also a p90 set also stock) and I feel the difference is well presented in this video.
If you canīt really make out a difference or do not care for it, well that is just well then.
For me I notice a difference and it is one that to me very personally just feels wrong. BKPs still make it sound awesome, but for that SC sound I get from those positions I donīt mind the hum and want that full SC response and not the one of a semi humbucker.
I do wanne emphasize again though that you should make up your own mind about it and use your ears as one is not worse than the other, it is purely a matter of taste.
Perhaps you can say the RWRP is a bit more modern in sound while the stock is more classic.
To me it just is a bit like covered vs uncovered (though I feel stronger on the RWRP/stock). While I prefer the covered look, at least on the bridge I just feel that the cover takes that little bit of life away in the sense that is makes it more round. Can be great for what I want out of the neck, but not on the bridge. Again that is just me.