Wow- a controversial topic. Who would have thought?
In 1990 my first solo was in a PA12. I did full stop, taxi back per the instructor's wishes. I was equally able to do a full stop or a T&G. The positive thing about the full stop, for a first solo, is it gives the student a chance to take a breather between circuits. The task by the time the student is ready for solo is easy, but the psychology of flying by yourself is new. The other thing about full stops - it is the first solo, it is a special moment meant to demonstrate and develop self-confidence. What is the rush? Just as an experience I think the full stop gave me time to appreciate the moment.
-- IFMU