You can find a comparison chart here:
Digital Volcano Digit Vaporizer vs. Classic Vaporizers

The warranty on the digital isn't as good as the classic, but the classic doesn't have an automatic shut-off. The digital costs $130 more than the classic, has better temperature control (not that big of a difference though), and can go a lot lower in temperature than the classic. Though you aren't going to go any lower than the classic for the purposes that volcano users on this form would use it for. I have a classic and don't see any reason to upgrade to the digital, except maybe it looks more futuristic.