My arguement is just that Opera has excellent rendering.
It's good, but it is not as close as being CSS2 compliant as Firefox is. Would be my second browser of choice as it is rich in features.
Even FF isn't perfect:
Firefox market share
by version Firefox 1.0 0.39 %
Firefox 1.5 0.69 %
Firefox 2 13.75 %
Total 14.83 %
Although Firefox 2 does not pass the Acid2 standards-compliance test, development builds of Firefox 3 do.
Edited by Major Payne, 23 November 2007 - 11:44 PM.