Not sure what SWT.BORDER would add, but I could add more info on the layouts.  Tall Button is "taller" than the Wide Button (but it's a relatively small "taller").  What it really means is that in a gridlayout if you set the boolean for grabExcessHorizontal/Vertical space it will try to fill out the client area it's given (in that dimension).  In this case one is a tiny bit taller, one is a tiny bit wider.  That's all the space the control is allotted by the layout.