When you insert a table in NWE, you will just get a 2x2 table. If that's not the size you want (and in most cases it isn't) you have to manually add rows and columns, and adding columns in source mode is difficult (unlike in visual mode).
So if you need a, say, 5x5 table, the tool will help you if you don't know the exact table syntax, but otherwise it's more or less useless, as you have to code the table more or less manually anyway.

In contrast, the table tool in WikiEditor shows you a dialog first, where you can select the number of rows and columns, and some other stuff, and will then insert the table.
I think this makes much more sense for a source code editor, as the generated table will fit your needs much better.

So NWE should have a similar dialog to insert tables, instead of the current default table.