I'm not sure of the specific chemical differences in the composition of the new vs old paints. The showroom cars of today use a thinner basecoat and a thicker clearcoat than the early 90's cars. The pre-90's cars simply had thicker paint. As far as overall durability goes, that is more dependent on lifetime care. With proper or inproper care you can burn a finish overnight or make it last a 1/4 million miles. (or more) Any bodyshop that is well versed in MB should use paint that is very similar, if not identical, to your car's finish. There are always bad/cheap bodyshops, but ask around your local MBCA chapter and find out who they recommend. As far as I know, Meguiar's does not use silicone in their exterior treatments. If you have had a panel recently repainted you will not want to wax for at least a month. Wash all you like, just don't wax for the first month.

Hope this helps...Lee