That's a valid opinion, I don't follow the p&s market, so I really don't know much about them. I was just pointing out the ridiculousness of a clueless salesperson, trying to claim one is better then the other with absolutely no reasoning behind their opinion at all. Since most p&s will never print bigger then an 8x12" I think you'd be hard pressed to tell the difference between any of them when viewing prints. Which is also why I think these p&s with 12mp+ are ridiculous. 90% of people don't need that kind of resolution in a p&s, all those extra pixels do is force you past the diffraction limit in anything but bright daylight. I'm convinced a 6-8mp p&s would deliver better all around image quality, then a 12-14mp with the same small size sensor. The whole megapixel race in the p&s market is just a marketing gimmick.
100% agree. I shot with a 3.5mp Canon D10 for a couple of years. I routinely enlarged sports images to 20x30 with no problem at all. It's all about the original clarity of the image and then what you do with in Photo Shop before sending it out to the photo finisher for print.
The part about Nikon color rendition is interesting to me. I'm a Minolta/Sony shooter, and on the forum I look at to buy and sell gear, I have read of at least 2 folks who switched from a 5D mk2 to a A850/A900 because they thought the Canon color rendition was poor. These were mostly landscape shooters though, you may be after something completely different with weddings, and sports.
I can't speak much about Minolta/Sony, they just simply are too rare a bird among professional photographers (especially the sports/journalist guys that I have the most contact). The Minolta/Sony bodies just aren't very popular with the pro shooters. Not having spent any time with one in my hands and not knowing anyone who uses one professional, I can only take your word for it. As for the color rendition on the 5Dmk2, I couldn't be happier with mine. In fact I can give you a comparison of the 5Dmk2 against a Nikon. As it happens, Disney has a small army of photographers stationed all over their parks now days. You get this card that the photographer can scan after he takes your picture, then you can view and purchase the photos on a web site later. Interesting concept, although the quality of their photographers is sketchy in my opinion. Anyway, we were there for 8 days in January, and I dutifully let the Disney photogs do their jobs. Primarily out of interest in the entire process and how Disney was offering photography services on a truly massive scale. Anyway, I bought the CD of all of the photos that their photogs shot with their Nikons (D90s maybe, didn't pay too much attention to them honestly). Well, as it happens, I was taking the same shots right next to the Disney guys. Let's compare the Nikon with my Canon 5D...
Nikon

Canon 5Dmk2

Granted, my camera body was a much higher end model, and I only shoot Canon L glass. But do you see how mucky the kids' faces are in the Nikon shot? Compared to the Canon? I see this same almost smeary look from guys shooting top end Nikon with their top line glass. It's hard to put into words really. It doesn't seem to bother most of the newspaper guys, but their end product is printed on the crappiest of crappy newspaper, so maybe they just don't care.
That said, be wary of color opinions from Landscape shooters. Those are the guys who are most likely to be carrying an entire bag full of filters. They often are working to alter the image colors more then capture true life color. In my opinion, I'd pay more attention to what the guys shooting macro still lifes of flowers think of color rendition. They're the ones looking to capture the full saturation of colors in their images.
For me, the most important thing with color rendition is that the image looks how the real scene looked to me, Especially the skin tones.
Here's a street performer in the Italy section of Epcot. He looks exactly how I remember him. He was wearing a bit of pancake make up.

And a shot at Epcot, handheld by the way at ISO 6400 on the 5D

And of course the castle, also handheld at a high ISO

It's all in the eye of the beholder I guess. I figure lenses have as much to to with the color you get as the sensor does as well. When I switched from a Sigma 70-200 2.8 to a Minolta 80-200 2.8, I immediately noticed a difference in the color rendition between the two. When I use that Minolta 80-200, Minolta 50 1.7 or Carl Zeiss 24-70 2.8 I rarely do any color adjustments in Lightroom. But when I use my Sigma 90 2.8 macro, or Sigma 150-500 5.6-6.3 I get completely different colors, more muted I would say, and I end up tweaking the saturation and vibrance in Lightroom.
Lenses are HUGELY important! I bought a few Tamron and Tokina lenses when I was getting started and poor. Garbage! I won't buy anything but an actual Canon lens ever again, and most likely won't buy anything but L series either. The image clarity, color clarity, and even more important for a sports guy, the focus accuracy and speed are simply no comparison between Canon lenses and third party lenses. That said, I have never owned a Sigma so can't really comment fairly. I just know that in my opinion, I have never seen a third party lens that was worth buying, even though it may have been half the price of the same length and f stop Canon lens.
Better off buying a cheaper body, then buy the good glass. That is if you have to penny pinch. My theory is get the top line gear, and write it off on my taxes!
I believe you only shoot Canon glass so maybe you get more consistent results then me.
True, Canon only. I would say that you are experiencing what can be a wide variation of quality when switching from third party to the expensive glass. Also. lenses like the 150-500, with such a broad reach, are notorious for that muted almost hazy look to the color. Sometimes they will have one length that produces a really nice image, while the rest of the reach is sub par. I would wager that on the 150-500, maybe somewhere in the neighborhood of 300 is a sweet spot. You'll have to look for it.
You'll find that most pros are using mostly prime lenses (single length), or very narrow zooms. I only carry two zoom lenses, a 24-70f2.8 and the 70-200f2.8. Everything else I use is prime. I would suggest staying away from those really large zoom ranges on lenses.
Now with the Pentax SMC lenses on my 6x7, and Velvia 50 inside. Well... I still think no digital (short of a $20,000+ MF phase one, or leaf back) can touch that as far as gorgeous colors, perfect transitions, and just plain awesomeness.
My A900 gets close as far as resolution, but I still prefer the overall look of the Velvia, it's just becoming a PITA to get it processed around here. 
Film is dying. For better or worse. Personally, I haven't shot a roll of film since June of 2000. From a purely business standpoint, digital trumps film in every way.