I'd say the wider 225/40 18's had more grip on the fast, sweeping bends (A road surfaces), but not as much agility or acceleration as the 205/55 16's due to the extra 'unsprung' weight. The 16's are also best for country, B type road thrashes (not as crashy).
Next up for me to try, are some 17's with 215 45's on.
