Speed difference yes, but it is so small that it is of no concern. When I say that it is faster we are talking about electrical signals having to travel less of a distance, ie a half of an inch less to the motherboard..lol. So to contradict myself, no, there is no speed difference.
The advantage of slot 1 as far as I am concerned is that you can use a bigger cooler. If you have a motherboard with both (Tyan Trinity 400?) Then I would just use the socket.