In the browser or a PC/Mac stand alone player?
The optimization is just that, it optimizes the speed for the best picture. Depending on which Slingbox and what you are using to watch on it will optimize to give you the best picture without over using bandwidth.
More bandwidth does not equal a better video there are other things that come into account.
Do you have an issue with the way it looks now? If so then there are ways to trouble shoot that.
What I understand from your post, is that you're having problems with the connection from a remote location.
In this case, you can check the following links which explains the possible reasons why you're having that problem.
Now, in case you're using the Sling Player software, then check this one.