Octaman,
Your response indicates your degree of attention to the decision, which is a good sign you'll be pleased whatever your choice. The reason is ... close study means you're less likely to be surprised.
Yes, the Suzi 50 has a lot more technology in it's architecture, but both motors have the same EFI. The 50's fancy valve train has been in the market since model year '98, and used pretty widely on Macs, without any reports of complication here. The 70 came out one year earlier, also with no frustrations that I've seen - those are pretty good records. However, a couple of owners reported a problem with temperature sensors (both 50 and 70 were affected) that have failed prematurely. Since this affects the response by EFI, you end up with a complex diagnostic problem - dealer accessibility within your area is advised. I think that was likely a supplier defect that's been cured for newer motors.
The TLDI motors have had good owner feedback too, though I think they've been out for fewer years. But the same would apply regarding a dealer. Somewhere within a one day drive will make a "good insurance policy". I prefer the 4-stroke, but then my guiding criteria was comfortable, quiet cruise. The Suzuki are reported to be the quietest outboards in the market.
Finally, you're correct that my DF60 is nearly identical to the DF70, so why pick the 60? As I studied them, the 60 had a max rpm of 5,300, and the 70 had a max of 5,800. Since I was mainly interested in mid-range performance, and since the 70 was $700 more in price, I just took the smaller rating. I figured I could always modify it to run to the higher rating if it was really necessary . . . I'd probably just get the 70 next time.
Best wishes in your search!
