Beta tests aren't better when many people play them out of the reach of the developer. The effects of a beta test vary.
It's highly inefficient to only let a bunch of people have a go at things. For beta tests to be productive they need to be controlled upto a certain extend. People need to play in different areas to cover as much of the game as possible and should play in different style also, use different avatars. Try things an 'average' player never does, use silly (but acceptable) combinations etc. etc.
All in all testing is a skill and from experience I know that real good testers are hard to find, as such I think it would be wiser to test in-house, atleast in that case you have some control over the testing to make sure most of the stuff is covered in the tests.
