I didn't know about UltraEdit - just tested on my files that I work with: 50MiB of ASM.js code in ~20 lines.
UltraEdit is very sluggish - to the moment it's not usable to work with.
I did a very subjective comparison between few editors in terms of speed in working with such file (flow is: open, find, manually edit, save).
And in my eyes here is the result:
1. Cuda Text
2. Sublime 4
3. VS Code
6. UltraEdit
Please note: I only tested the workflow that I work on daily basis. I can see that UltraEdit can do much more that Cuda Text, and in different test cases probably it will be a much better choice. But not for me.