I'd say its difficult, if not impossible to accurately compare the two countries, with the difference in laws, penalties and attitudes. But IMO there's probably not much to call between the two, we have a roughly similar range of social strata and class distribution and we're lucky enough to be '1st world' countries.
You can use the stats here:
http://www.met.police.uk/crimestatistics/ to see what change there's been in the London area of the last few years, but even that's skewed as they frequently change the way the stats are recorded.