We're not dead . . . yet.

The best of any used Mercedes is one that has been maintained by the previous owner(s) and hopelfully has the service history and records to show the work done.

All things being equal (service & mileage), your best bet for a daily driver is a 1993 (last model year) 2.6L model. M103 headgaskets can get leaky after 80K miles, so be aware. There are still 5-speed manuals out there, just fairly rare. The 1993 would also be the only year for the "Limited Edition" model, only 700 marketed in the US, while the 92 and 93 2.6L has the "Sportline" option package (suspension & trim), which was included in the Limited Editions.

Why a 2.6L? Nearly the same performance as the 2.3-16 in a smoother, easier to maintain form. The 2.6L is also the preferred engine bay to drop in a larger displacement motor, like the 3.0L or bigger M104 variants.