I would say SA-MP Map Constructor, as it lets you remove world objects directly, and the place ment of objects are 1000 times better than MTA.
The placement is 101% accurate.
What's wrong with object placement in MTA:SA map editor?
If you are looking for a quick-to-use interface then pick MTA:SA editor. If you are looking for a more detailed interface, go for the SA-MP constructor.