In my humble opinion/experience:
Yes, MK Is do sell faster and for more. It may be a factor of the MK II being introduced first and all of the initial cars being MK IIs, the MK I market had to play "catch-up" or it may just be what has been offered for sale.
The "fire sale" cars are gone. There were several rollers and completed cars that sold WAY under market for various reasons. Some were sold by people who bought the "new, hot, thing" and decided it was not for them, some were collectors who rotate cars often and some rollers were sold by those who never completed them or bought as an investment (always a bad idea!).
You will not find a driving SPF that is not wrecked and is properly done for under 125-130K now and many will be well above that point. As the wait for a new chassis is over 10 months instant gratification will cost you. The roller price increases also help drive the existing car value up.
Except for unusual circumstances (i.e. BJ auctions and other venues where these cars are not understood/apreciated) the "bargains" are gone.