Like Missioncoonery, I've also been around both a lot.
Like both a great deal. In terms of companies, you're dealing with excellence on either side. When it comes to heat, the V4s are definitely warmer, though certainly not to the point where it should be a concern. I own amps that run hotter.
Sonically, it's really a case of them being very different products. The Manleys are more engaging, upfront and brash. The Quicksilvers more romantic, lush, and rich. Personally, I really love the V4. If I could order the Snappers with the triode option, things would be closer though I might still opt for the V4. For what people traditionally expect out of a "rock" amp, the Manleys get the nod.