Typically in windows the ok / cancel buttons are on the right of the dialog. While I dont think this matters a great deal, its nice to be consistent. I think it also helps to show that the buttons relate to the dialog rather than being part of the dialog content.

When implementing this in #6189 I found that the buttons didn't cope with the resizable dialog very well when aligned to the right, this may be a limitation of the wx framework.
Try putting the buttons in a panel first, see http://zetcode.com/gui/wxwidgets/layoutmanagement/