I think the cleans on the DIEZEL are nice but not phenomenal. They are in the "hey that's great for a high gain amp!" The Shiva gets a clean that makes you almost go F*** let's play a Jazz gig. The Reverb is lush.
The DIEZEL has its own brand of fat, high gain. It's kinda like uhhhhhhhhh crap how do I say this? It's got an original sound. FAT, yet not mushy, NEVER BUZZSAW, powerful, VERY CHUNKY. I only criticize that I hear it as more saturated than say the sparkly crunch of a JTM45, should you want that old AC DC sound. If you want that level of freedom, go Bogner Ecstasy. If you want modern that can play in the new music vein while holding a harmonically rich classic tone - go DIEZEL. They are such different amps - so you have to decide by what you want in responsiveness and style of music.
The Shiva lacks modern features such as switchable loops etc. midi blah blah blah