those who have the MSO say that the interface is much slower and clunkier than that of the DHO.
I have both the MSO5k and the DHO1000. Sure, the 5k UI now looks a little dated as compared to that of the DHOs but I find it perfectly useable in absolute terms. I don't perceive any lack of response, not to any significant degree. And as it has already been said, the physical vertical controls I actually prefer, at least in my workflows. It could be increased familiarity (I've had the 5k longer) but I actually find the 5k faster to use sometimes. YMMV. The DHO screen is noticeably brighter, which is welcome but it's also significantly more reflective, so it's a mixed bag.
I initially bought the 5k rather than DHO, since I also am working predominantly in the digital/microcontroller domain. My rationale being that the best bang for the buck comes from buying features you will benefit from e.g. significantly increased sample rate rather than those you won't e.g. 12-bit resolution. Unless you're planning to work with small signal levels, the front-end noise argument is moot imho.
Also, you're likely younger than I am and may hence have better eyesight but - I'm glad I went with 9" and 10" screens respectively. MSO operations with any significant number of channels on a 7" screen would be pushing it I think, at least for me. You can, of course, always make use of the HDMI output on any of these machines but only if you want a monitor on your workbench too.
I'll add too that the reason I subsequently purchased the DHO was "because I can" and "it was cheap" (40% discount during Black Friday week) rather than needing to make up for any deficiency in the 5k. It could still find it's way onto an auction site yet.