The board rules here state that you should always use the same posting name:
http://www.behindthename.com/bb/baby/help#rules
The first time I saw
Saxon I didn't like it at all. It made me think of invading armies, and seemed a bit trendy, like
Jaxon. But then I looked it up and found that it does actually have quite a long history of use as a first name, albeit a rare one. Since then it's grown on me quite a bit, and I think it would be an interesting choice.
Saxton's not so appealing - just seems like a last name, and the -ton ending is very trendy.