The UI are similar but not exactly the same, the screen regions and global ergonomics are very close. There are more options in DPS (it's normal, there are more features), DPS UI is white on black and menu text size is fixed, unlike DPO where, as it runs in a web browser, you can zoom in and out the whole interface.
Here is a quick video of DPS, of good quality I think, where you can get an overview of the ergonomics : https://www.youtube.com/watch?v=FQm4sbCqSBY
I am not a Dungeon Painter specialsts though (I bought it when it came out to support the software, I think it is a good tool to quickly create encounter maps in just a few minutes but I don't use it that much), feel free to ask more precise question directly in the software forum on Steam, it is fairly active and the devs are responding quickly.