hmmmm, I've been using reasonable quality rf and slr systems for quite a while and still can't make up my mind which is better!

Don't think it's possible to answer it in a simple way. You said: expansive landscape images with tripods. Yeah, I know: convention says a slr with a wide angle on a tripod works best.

And yet this (click on thumbs to see larger): http://wizofoz2k.deviantart.com/art/S-for-sand-93569062 and this: http://wizofoz2k.deviantart.com/art/...aters-93569600 were taken handheld, late afternoon, with a mild tele - 90mm - on a ZM rangefinder, while this: http://wizofoz2k.deviantart.com/art/...-hall-93569290 was a "cheap" Ultron 28/1.8 on the same body, same hands.

Not perfect, but good enough for me. Go figure?

I guess if I had to chose between my beloved Nikon gear or the ZM and its glass, I'd probably go with the Nikon: been using it for decades, while the ZM is only with me since 2006.
But one thing I do know: when it comes to low shutter speed handheld, the ZM is miles ahead: I simply can't hold slrs anywhere as steady.

At what point then ultimate lens quality becomes the deciding factor is something I haven't yet established. Although of course: I'm having a heck of a lot of fun finding out!