MTA is and will always be better than SAMP.
Map editor, lua scripts, custom skins and models, you can edit and mod more things, etc.
Making a MTA server based on bully is not a bad idea, I mean, after all it's better than nothing. I know that the gameplay will not be the same, but I still want to see how it would look like.
If you want I can provide some files for the server if you are going to make it.