I am considering buying a 560SL but seeing that prices for the early 90's 500SL's are similar I wondering if I would be better off buying one of those. I have no experience maintaining my own cars so my interest is in getting the model that will cost the least to keep in running condition. I greatly appreciate the styling of the W107 and realize that those in this forum might be (a bit) biased towards it. I was a big fan of the 500SL when it came out but have to admit it is not aging as well as the earlier cars. My concern is that the W107 is a 35 year old design that may be harder to maintain than the more modern mechanicals of the 1990's model. Please also note I am looking for a weekend cruiser not a daily driver or show car. All opinions are welcome but I would especially like to hear from anyone that has owned both models. Thanks!

After having owned and modified several different brand cars I would say you may want to gain some experience in doing your own work.
A older car requires adjustments, tinkering and repairs of worn out parts. Keep in mind that age as well as mileage both play a factor. Rubber and plastic dries out and gets brittle even if the car has low mileage...ect..

Example. My 1987 560Sl has low miles. I had two bulbs in the dash instrumentation burn out. I decided since two died I would replace them all. Only $20 in parts, but I had to tear the entire dash and center console apart to replace them all. Had this been done at the dealer labor would have been through the roof!

I am now replacing a under-hood pad. The old one dried out and is shedding.

I think the 560Sl is a simpler design than a newer SL500. Less to go wrong perhaps. I would also think a 560Sl would be cheaper to maintain.
Keep in mind that both cars are older and they will require work now and again. If you chose to have them serviced at the dealer both cost the same for hourly labor and parts for both are equally expensive.

there is still a good parts supply for the 560SL. for how long I do not know?

The 560SL (107 body) is of course older design and older technology, but a *MUCH* simpler vehicle to diagnose and maintain. You'll want to do a lot of surfing the BBs and familiarize yourself with its usual failure modes, quirks and specific needs.

The 129 is a couple of decades newer in its design but much more complex. The most stellar, and most frequently troublesome, example is that fully-automatic top: Instead of a few manual latches and a rather simple lever-and-link system, it's got (if memory serves) fifteen hydraulic rams and over twenty limit switches with a computer module running it all--any one of which can go wrong. Check threads on rebuilding the hydraulic rams in the windshield header, one on each side, that work the header latches automatically--and when you're looking at a possible car, check for old hydraulic fluid stains down the A pillars from when those cylinders leak.

Either one is getting to be an old car and will need things like new suspension bushings, new brake lines, etc etc eventually. Either one is much more reasonable to own if you can do at least some basic DIY, but the 107 is much more DIY-friendly. Neither is going to be anything like the simplicity of, say, a 1973 Mustang (I know--I had one), and they both have distinct quirks. Either one is easier to live with if you've got a good indie mechanic who's not quite as rapacious as the dealer to help keep it going.

My 0.02: Parts (any parts, tune up, body, weatherstripping) are MUCH more expensive on a 129. Much. Check out the price of the distributor cap(s!) on a 129 500SL. Even if you do the work yourself, the TCO is much higher, in my opinion. On the other hand, there is absolutely no question that a 129 is a "better" vehicle - and it "better" be, with almost 20 years of engineering improvements in it over the 107.

If you can find a prime condition 380sl or 450sl
with service records,those are great cars too.
They generally cost a lot less and you can have
just as much fun.

Thanks for your great feedback. I'm still on the fence about whether or not to take the plunge but if I do it will definitely be a 107.