I done ridiculously extensive building in both. We had written a lot of custom sphere scripts to let us do specialized things as well like coloring based on item number. Deleting based on z level, etc. When I first switched to RunUO it was a difficult transition. There were so many things I couldn't do any more (or thought I couldn't). Now I would never consider building in sphere. The tools for runuo are amazing. The freezing and unfreezing on the fly, Pandora's Box
http://arya.runuo.com/ is amazing. It does everything Axis did and more, and it all works. There are so many things that I can do with RunUO that I could never do with sphere.
The command that is difficult to understand but is so incredibly powerful is the "where" modifier. It works with most commands, including the single, area and global modifiers. I'll give you and example or two using the area selector.
[area set hue 1234 where item itemid >= 2345 itemid <= 2355
That will color every item within the targeted area that has an id between 2345 and 2355.
[area inc z 3 where item z == 20
That will nudgeup by 3 any item in the targeted area that is currently at z 20.
[area remove where item itemid >= 1000 itemid <=1005 z == 25
removes any item that is from 1000 to 1005 and is at 25 z. If it's at 24 z it doesn't touch it.
I could go on and on. The one thing that really made me cheer, the area targeting goes right on the range you select unlike the old nuke commands in sphere where you had to be one x and one y over.
The only feature that I have not been able to duplicate is the tiling multiple items at once in a pattern. I suspect I just haven't figured out how. I miss that feature for doing random looking floors.
The learning curve for RunUO is steep, but I personally am glad I made the change. I held on to sphere for many years and sometimes still feel guilty for abandoning it, but only briefly. I do still miss the ease of scripting. *sniff, sniff* RunUO coding is powerful, but really too complex for non programmers.
Good luck with your building rage88.