I've got a Dell XPS 12 and can only recommend getting an Ultrabook like this one. Yeah it is expensive and yeah it definitely had its quirks in the beginning.

I've got a Dell XPS 12 and can only recommend getting an Ultrabook like this one. Yeah it is expensive and yeah it definitely had its quirks in the beginning. However performance is crazy, I'll get easily 6hrs+ battery life on programming workload (in energy saving mode of course). I have no experience with passively cooled Core M processors or the cheapo tablets you are currently considering, but having a full Intel CPU inside this horse is definitely noticeable. If you have any questions, I'll be happy to answer