My personal opinion from owning a ClassicLine6 original amps a Spider I, and III , a POD and now I Gig with a Spider IV 75. The Spider IV has been the best for me. I do think the SpiderValve MKII might have a sweeter tone due to tubes. But I will say without the editing software and the FBV board I never could have dialed in my amp like I can now. I cover a large range of styles so the versatility of the Spider IV with its compressors and reverbs that I didn't have before on earlier models makes it the best solid state /digital in my book I'm a LINE6 believer