I can probably add some insight, hope this doesnt wind up confusing you more:
My first leica was a CL and I got it because of the 40mm lens and viewed it as an upgrade from the fully awesome rollei 35 which had a 40mm sonnar. I immediately fell in love with the camera and didnt take another photograph with any other body or lens for nearly 8 months after getting it. The camera has hands down, absolutely the best in camera meter of any body I have used. The 40mm Summicron is easily one of the most under estimated leitz lenses. The 35mmv4 cron, which people swoon over to the point where the lens has its own stupid pet name now, is really only marginaly better that the 40 cron. It IS a better lens, its positively sharper wide open, but the signature is so close that it is truly odd to me that it costs 5 times what the 40 cron does. If other M cameras had 40 frame lines, the 40 cron would likely be selling for somewhat near what the 35mmv4 cron does they are so similar. I have both, like both but would easily chose the 40mm if I could only keep one.
The CL definitely peters out at 50mm, this is not a great body for a 90mm lens. The finder is nice enough, its easy to use, the metering is easy to see and never gets in the way. The film advance is fine if you dont know anything else, if you have other M's it's definitely made in Japan. It doesnt feel cheap at all, it just doesnt feel like an M3.
I was intensely productive with my CL and couldnt imagine parting with it.
After reading this board and others, I soon began to feel left out and my next body was an M3. After getting that, I realized what everyone was talking about. I still used the CL predominantly.
I still felt I needed to acquire more gear after reading everyone talking about how amazing the M6 was, so I got one, the last production run of the classics with an .85 finder as Im mainly a 50mm guy.
Succintly, I despise that M6. The meter is esentially the worst meter of any camera body I have ever used made by anybody. And I dont say this to make a poetic comparison to my statement on the CL meter. The meter in my camera isnt broken, its just terrible in function. Absolutely useless in any kind of back lit scenario. The LED's in the finder didnt so much drive me nuts while I used the camera, but once I went back to meterless bodies I realized how unconsciously distracting they were. I dont think it detracted from using the M6 but Im relieved to not see them in my other bodies. My M6 no longer has a battery in it, its a slight improvement.
The finder in my M6 is not the least bit accurate. If you compose in the center of your frame it wont be an issue but if you like to frame with one object in the left hand corner of the frame and another in the right, the finder just isnt accurate enough to do it. I can tell most of the photos Ive taken with the 6 because there is always something oddly cut off on the left or right. I dont see this with my other bodies. The finder also has way too many framelines, which I guess is wonderful if you change focal lengths five times a day, but just simply annoying any other time. Sure you get used to it, but Im probably never going to have a 75mm lens, so why should I be burdened with seeing those lines all the time. Annoying. The frame lines are also too thin for my taste, I find the 2/4 lines to be perfect.
The film advance of the camera is nice, certainly nicer than the CL but IMO doesnt really at all compare to a nice M3, M2 or M4. Its just not on that level. It sure is close enough, but if you want to nit pick, the body is just not as nice as an older body.
My comments on the meter in the M6 and the finder on the M6 should probably be weighed with a grain of salt depending upon the type of work you shoot. Certainly you dont see this opinion very often and I absolutely do not doubt that I am in the rare minority thinking this way.
If you are into shooting with a 50mm I would suggest a return to the M3 as there is nothing like shooting a 50 (or a 90) with an M3. I usually wind up composing my shots with an M3 slightly differently than I do with an M2 or M4. These days, my favorite body is an M2, the simplicity of the finder is totally freeing not having to look at other frame lines besides the one that is up for the lens. The patch is also seemingly slightly bigger than my M4 (maybe Im just imagining that). The camera is exceptionally well built and there is nothing quite as gratifying as the film advance on my M2.
confused? rad.
I would get a CL if you want to shoot with a 40, the lens is awesome. The meter is amazing if you know how to use a spot meter. The M6 is a cool camera, I tried so hard to like that thing, but for the reasons mentioned I could just never muster up any lust for the thing, it was a total buzz kill every time I pulled film out of the tank. You may not, however, run into any of those troubles, it doesnt seem like many people do.
Having a CL kinda misses the mark of "the leica experience" (whatever that means) when using it, its weighted oddly and can be a little fiddly, the shutter release is definitely its own thing, but the images you can make with the camera will floor you. They are cheap though. I feel like for the money you spend on an M6, for me, it always never had "the leica experience" either. I think if you use a 1960's M as your baseline comparison, both bodies will disappoint you. And if you dont you can totally fall in love with either, they just both have their own drawbacks. And of course no 1960's M has a meter and thats enough of a drawback for most people to not even care how incredible brass gears on the shutter cock feels. Someone said it before, the "leica experience" comes in several flavors and I think is definitely what you make it.