Even though this is sort of an old thread, I couldn't resist commenting on it. I have both cameras. I bought the Z2 after I thought I'd lost(or stolen) the 6490. Even though I REALLY liked the 6490 I didn't know 100% if I wanted to buy another one.
I started to look for a replacement and stumbled upon the Z2. After a reading 100+ reviews on it and a lot of other cameras I took the plunge and bought one. So far I've been extremely happy. As luck would have it I found my 6490 and now can compare them side by side.
One thing I love and hate about the Kodak is it's lithium ion battery. Incredible life but not quite as good as my Sony DSC85. That camera could shoot for a week without recharging a lot of times. Unfortunately you have no choice but to by the special battery. It definitely has longer batter life than the Z2 which is always running it's LCD. I do like the fact that if the batts are dead in the Z2 I can buy extras anywhere.
The other downside to the 6490 is you must use the stupid docking station to recharge the batter UNLESS you buy a special charger. The blasted station is too big to travel with so I had to buy the special charger fortunately it is 110/220V so I can use it anywhere. Most likely though the batts won't work in any future camera so you basically p!ss your money away each time you buy a new camera.
I have a solution, how about Li-On batteries in AA size? Then no more propietary battery packs that you basically throw away when you buy a new camera.
On to more meaningful comparisons between the Z2 and 6490. The EVF is better on the Z2 but the diopter setup sucks. However with the LCDs the Kodak has the best LCD I've seen on any digicam. It is big, bright and easily read even in sunlight. Since I don't usually use the LCD anyway it's not a big selling point for me but to show other people the pics it could be nice. I have a different system. I just pop my SD card into my Toshiba e805 and show them on a big 4 inch screen in VGA resolution. The Tosh has an amazing screen for a PDA and it does VGA in portrait or landscape modes!
The Z2 kicks the 6490's butt in video mode. It is not even close here. Hands down the Z2 is the winner here. Also for some strange reason even though both are QT format I can't see a preview still in Adobe Photoshop Album (1.0 or 2.0) when using the Kodak. Maybe something screwy about the header info on the vid. I've loaded all the patches too and it doesn't work.
I do like the 3:2 option of the 6490 in the 4MP mode. I don't have to do any cropping to print a 4x6 print. It saves me a ton of time. This is something I wish the Z2 had.
General print quality is pretty close. I think the Kodak might have a slightly better lens but it seems to have more noise. Color saturation is better on the 6490 but exposure is better on the Z2. Z2 is much faster to focus and shot to shot as well as startup. Maybe it's a little hokey but I really like the fake shutter sound on the 6490, it is very realistic and sounds like my Sony. Kodak was slightly better in lowlight condition but only fractionally. Z2 wins the flash contest. Definitely one of the best built-in flashes on a digicam. I love having the histogram on the Z2, wish the 6490 had it. Manual focus on the Z2 is sweet.
Overall feel is somewhat subjective. I like the Kodak better. I like the traditional look of it too and I can more easily fit it in my pocket. However I am not put off by the look of the Z2 and like it more each day. Controls are both pretty equally. I do hate having to see what the mode I've just engaged on the Kodak is good for. For example, when you select the sport mode, it gives you a little flash screen on the LCD reminding you what it should be used for. Overall there is more flexibility on what I can do with the Z2 vs. the Kodak.
If I had to choose and keep one camera, it would be the Z2 at this point basically for 3 reasons.
1. Movie mode is amazing (no lag on mine so far)
2. I love being able to use normal batteries. I travel a lot in foreign countries and you never know when you might have a dead battery even carrying spares.
3. Greater user control + histogram.
So if you are a beginner wanting a good zoom and more pixels, Kodak is a great choice. I want a more advanced camera with more creative control and not a wimpy 320x240 movie mode. Kodak did a great job on the camera and I really love it but the Z2 is better for me. You can fire up the Kodak and immediately get great prints. To really appreciate the Z2 requires reading the manual. Do that and you really will see the depth of features.
Just my impressions and they may change with more time on the Z2. So far I don't want to give up either of them!