If you want to sound just like John Sykes from the Whitesnake album, then the Mark III Red Stripe will get you there. To me, the Mark IV has more of the smoothness of the Mark IIC+. IMHO.
I can get the Master of Puppets tone out of my Mark IV. If you pick up a IV, read the manual. There is a section in there where they tell you how to get the IIC tone. It's not 100%, but 99% for sure. Close enough to smile at the extra $1500 in you bank account.