Merc,
the US spec engines make about 10 hp less than the Euro engines. The differences are a milder cam and differently calibrated injection pumps. The 1970/71 US cars also use different distributors, but the advance curves appear to be pretty similar. Final drive gearing is also different, with the earlier Euro 280 SL's having 3.92 diffs while the US cars got 4.08's. Round about late 1969 or early 1970 production (maybe at the model year break point?) the Euro diffs went to 3.69 and the US diffs went to 3.92. The gear ratios aren't hard and fast because there were optional ratios available for a while, but in the US optional ratios were unavailable for the last year or two.
There are also a number of cosmetic differences, like hard door pockets in the Euros vs soft pockets for the US, plus several more things.
Unfortunately, the Euro cars also tend to suffer from rust problems more than the US cars because of the use of salt on the roads.
George Davis
'69 280 SL Euro manual