Nothing about the HD598 resembled anything remotely close to warm, and this is off various sources, and a neutral amp. It is close to neutral, so if you pair it up with a warm amp, I can see it change to a warm headphone, but its inherent sound signature is lean on bass, very rich in mids, and treble emphasized slightly. Its the most un-Sennheiser can out of the typical Senns outside of the HD800.
The K701 is also inherently lean on bass, mid rich, and treble emphasized slightly.
The headroom graphs also show just how close they are to one another. Not that graphs mean anything, but it is worth noting how similar they are. I'd post it, but I'm on a phone.
I do agree that the K701 is definitely analytical, while the HD598 is less so, but I put them both on the analytical side. A K701 with warm flavoring would sound like the HD598 off a neutral flavor of amp/source.