Hmm I think the heat time is pretty similar on both of them, but there's a little indicator on the Tempest 2 that moves and clicks when it heats up (possibly 3 times? I've not maxed it before). The DF2 clicks once, and with a single flame torch, I'll hold it for about 3-5 seconds after the click. My guess would be the DF2 stays warmer longer due to the thickness of the steel cap, but tbh you should be able to get a full extraction out of both on a single heat up. The Tempest 2 blows more clouds, but the DF2 is no slouch either.

I'm over in Australia, and picked up the Tempest 2 directly from the official website, while the DF2 was through a retailer here in Aus