If your going to buy a new VMP blower get the R for a couple hundred more. If for any chance you want to go bigger you'll have a used IIR and probably get a good return. Plus it's just a better design. If your looking to save money buy a used Gen II
$2800.00 GenII
$3300.00 GenIIR
$500.00 spread. I'm keeping the $500.00 because on PUMP gas, there is not going to be that much HP/TQ gain between the two, if any.
Just my own thoughts and what I want to do with my wallet