When I bought my R129 last year I was in need of a daily driver, for want of a better phrase, as it was to be my only car, I use a scooter to commute and a 1000cc bike for my speed fix. After a lot of consideration and advice from this forum, some of which I took on board and some such as going for the 500 I ignored, I bought a 2000 SL320. I went for the V6 as it's generally considered more reliable, and it is very smooth, and it has a few things such as xenon lights & memory seats that I wanted.
I did buy it on condition, it wasn't perfect as it needed new front wings and a new soft top, but the rest was sound. It had a full service history, not every receipt but a fully stamped up service book, and the MOT history checker showed one advisory in ten years, a discoloured indicator lense. This to me implied that the previous owner(owners as I'm the 5th) had kept on top of the maintenance rather than waiting for things to get shown up on an MOT.
I've had the wings replaced with new Mercedes ones and the roof is booked in for a KHM soft top to be fitted at the end of May. The car will probably stand me in more than it's worth by the time the roof is done, about £7500. It's not concours but very clean and tidy and I love it, it drives very well, still pretty well composed on spirited B road driving.
Should I have bought a 500, on aural pleasure and probably on later values perhaps, but the SL320 V6 was my choice and so far I haven't regretted that choice.