Bob,
Well, leather or vinyl...
Why don't you just stay with the the cognac vinyl in your car for a while and decide later? There is no need for a rush now.[:0]
As to leather ...
... it only makes sense if you go to as close to orignal Mercedes-Benz quality as possible, i.e. GAHH quality or better.
The texture must be correct (not too much, not too less), the color must be correct MB, not too glossy (like bacon speck) and especially not too flat, it's more of a semi-gloss which is original. The basket weave pattern is most important; I have seen lots of interiors which look close to correct but are actually not, and especially the quality of the sewing is very important for a good (perfect) result.
In Germany, where most pagodas have (converted to) leather nowadays, there are immense quality differences visible. Ed Cave's results were already quite correct ...
So, if you want to go for leather - search for the best one and not for a reasonable quote.
But basically the same is true for MB-Tex !
Well, I personally prefer leather in an SL.
Why? Because it's an SL and not a truck or taxi-cab.
The appearance of 30 years old but very well-cared for slightly patinated leather without damages is just overwhelming. Nothing can top that. That is the classic appearance and touch which most originality aficionados prefer.
Look at these cars next time on a car show with very-well cared interior! Mostly sedans and coupés are the better candidates.
Most impressive is the smell of old leather in a car. You can never achieve this with anything else, especially not with a leather jacket or pants or so. Perhaps with a special spray with the smell of leather ...
Unfortunatley even new leather smells (quite) different than this old plant ingredients-tanned leather of those days, strong, powerful but not moldy...
Leather makes (especially a top-end car) much more valuable, it's noble what vinyl never is.
Personally I like cognac leather (color 8006, interior code 250) much, it looks way ahead of cognac vinyl (ask how I know, but my 114015 knows!).
Just to make your personal decision harder ...
OK just my 2 cents ... or 3
Achim
(Magdeburg, Germany)