Snappiness, responsiveness and resource-sapping
For general use, it's tricky to differentiate between the browsers on test.
All performed acceptably on a range of websites. Also, all browsers, when new, tend to feel faster than ones bogged down with your browsing history.
Typically (but not always), the WebKit browsers (iCab, Safari, OmniWeb) feel a little snappier and Opera a little slothful. Firefox generally suffers the most over-extended use, slowing up after a few months.
In terms of resources, Safari is the heaviest browser regarding RAM usage, followed by iCab. None should tax a relatively modern Mac, however, unless you have dozens of Flash-oriented pages chugging away in the background.
When it comes to benchmarking tests, Camino's dated guts are lacking regarding compatibility with modern web standards and scripting speed.