50 is a tighter unit and with constant use, it wont take long to adjust to it. It has great speed and res for composed shoots. 550 shoots HD video, and is more an all round unit for all types of shoots(and is definately sexier) but for the extra dollars, the 50 feels more of solid unit. Go have a play with em' at a shop cause the 50 is a bigger body (so its perfect for my clumsy boy hands)
i fucking want one!