Really different.
The Classic with the red Fasel:
Thicker sounding. Toe down isn't shrill, heel down to the middle position is way, I dunno, throatier? Growlier? It's got more gain, you can hear the circuit breaking up in the heel down position. It sounds like a broader Q, or maybe the extra harmonics from the circuit getting crunchy give it a broader frequency range. I think it sounds killer, especially since I use AC30s and my main guitars are a T-top loaded Explorer and Gretsch with Filtertrons; the standard gets peaky toe down. Looks like a DVD player inside - all SMD components, board mounted jacks. It is true bypass, though.
The Clyde:
Physically, really classy. Lighter case, smooth pedal action, feels like a few more degrees of motion. Circuit's nice and simple - case mounted jack sockets, full size components on the PCB. Where the Classic is rough, loud and throaty/ crunchy, the Clyde is precise. Volume feels perfectly balanced relative to bypass sound, and from heel to toe the vol is consistent too. There are no dead spots or heel drop off, which both the Standard and Vox V847 have. The Q seems narrower - it's a sharper, focused sound, really nice for chikka chikka stuff, so I think cleaner funky players, and maybe the Hendrix inspired guys, would love it. For my rig, it gets too bright toe down.