Although not a direct comparison to the 550i N63 engine, check this
link for tune comparison details on the N54 engine. As a general statement, Dinan tunes are less aggressive than others (JB4, Procede, etc.), mainly due to the more modest increase in boost levels. I had the Dinan Stage 2 on my 335i, and was pleased with the performance. If your primary concern is maximum gains in hp/torque, Dinan will likely rank lower on your list.
Good luck.
