I agree -- do a search and you'll see a ton of info and opinions.
Personally I think there are several good reasons for using synthetic in the 119 engine. These engines, at least when in the W124 chassis, tend to run on the hot side, and thus the extra protection of a synthetic may give a little insurance. Also, the timing chains on these engines are very long. Chains are said to "stretch" over time, but what really happens is each pivot point on the chain wears just a little, and the cumulative wear across the whole chain causes the chain to lengthen. I have convinced myself that using synthetic oil MAY reduce that wear and stretch and again may give a bit of added insurance.
I use Mobil 1 15W-50 year round.