We have both Kleen Kanteen and Sigg water bottles. My husband is an avid backpacker and hiker so we have done lots of research on water bottles and water purifiers. Also, after learning how polycarbonate plastics/Lexan (ex. Avent Bottles, Nalgene Bottles) leach Bisphenol-A into liquids we searched for the healthiest bottles on the market. After much research Sigg and Kleen Kanteen bottles seemed to be the best choice.

After owning both for over 2 years I can easily say Sigg is better than Kleen Kanteen on almost every feature I can think of to compare.

1. Sigg bottles are designed and manufactured with a significantly higher level of quality assurance than Klean Kanteen bottles. For example, the tops on the Sigg bottles have fine precision threading for a very secure and tight fit to the bottle. In stark contrast, Kleen Kanteen bottles have loosely fitting tops and their threading on the bottles usually doesn't match well to the bottle's threading. Also, the o-ring on the KK's tops can't always compensate for the looseness which can allow the KK bottles to leak quite a lot. KK's metal tops fit better than the plastic tops (sport tops).
2. Sigg preserves the taste of the water better than KK. The water from the Sigg bottles even after sitting outside of the refrigerator for a day still tastes pure. KK adds a slight metallic taste to water. KK's stainless steel is very good but Sigg's enamel coated aluminum is definitely better.
3. Both bottles seem to do a great job preventing leaching into a beverage as they both use non leaching polypropylene #5 plastic, but because KK gives water a slight metallic taste I think Sigg is slightly better than KK on this point too.
4. Sigg Kidds bottles have a better top cap to protect the drinking area from dirt and foreign matter.
5. Both Sigg and KK bottles get hot or cold depending upon the temperature of the beverage put into the bottle, thus the need for neoprene covers for both brands.
6. Both brands dent more easily than I want them to. On this point I think KK wins. The Sigg bottles dent slightly easier than KK bottles.
7. I think that KK bottles are slightly easier to clean because they have a wider mouth than the Sigg bottles. Both brands are easy to clean.
8. My son can drink just as well from both the Sigg bottles and the KK bottles.
9. Both bottle brands are light; Sigg is slightly lighter but not enough to mean much.
10. My son prefers the kid style graphics on the Sigg bottles; however the KK bottles have no paint on them to scratch.
11. Both Kleen Kanteen and Sigg water bottles cost too much.
12. We did get one large bottle that got light rust on the outside of the bottle. We threw that one away. The other bottles are ok.

From my experience Sigg bottles are a great idea precisely realized and Kleen Kanteen bottles are a great idea only approximately realized. If KK can improve their tops treading to match the bottles as well the Sigg bottles KK would be worthy of the high cost. For now, we are only buying Sigg bottles. 2 stars

I have owned 3 KK bottles for over a year now and love them. They all have the loop ss cap and have never leaked. They clean easily, are lightweight, and the water tastes great. They have been dropped several times, and are fine even though they have dents. I would reccommend these water bottles to anyone!

I'm about to purchase a KK sippee for my baby. After reading the review from the person comparing to Sigg, I decided to research the Sigg. After searching for over 15 minutes on the sigg.com website, I could not find any information on the composition of their aluminum bottle liner. I then queried the web and found the USA Sigg website (mysigg.com/faq) and this is what i found regarding the liner composition:

"The ingredients (like the formula for Coca-Cola) remain secret and unavailable to 3rd parties so as to ensure SIGG retains its competitive advantage. The key of course is that the SIGG liner is FDA approved and independently tested to be taste and scent inert - and resistant to any leaching (0.0%) so 100% safe."

I, personally, do not take corporations 'word for it' that something is safe, and by no means do I trust the FDA's standards. Saying something is secret definitely does not increase my trust. I am a hydrogeologist and have spent hundreds of hours testing water and reviewing lab reports. Simply stating that there is no leaching does not mean much to me. For ex, under what conditions were the bottles tested? -- Sitting in a hot car for hours, sitting in the sun, carried in a pack for hours, etc. These are real conditions for water bottle usage. In addition, why is there not a link to the lab reports showing what was tested for, when, and by whom? I would think this important information would be listed on their flashy website.

I am not associated whatsoever with Klean Kanteen or anyone else, simply a crazy researcher/mom trying to find information. I decided the Klean Kanteens are still the best choice - no mystery in stainless steel construction. According to KK website, "Stainless steel is easy to clean, durable, inert, sanitary, toxin-free, and non-leaching."

Lastly, the designs are not fancy on the KK, however their is no paint to peel (this happens on the siggs) which would be a hazard for my baby who puts everything in his mouth.

Consumer awareness is what pushes corporations into publishing important health information, such as materials & chemicals used (liner composition) and lab reports veryifying that something is indeed 'safe' and has been tested adequately.

Don't let my opinion convince you, you be the judge...
5 stars

I just received my Klean Kanteen - probably the 15th I have purchased. I own a couple, and have given many as gifts. But alas, the company has done a bait & switch with the caps. What happened to the stainless steel caps??? They used to come standard. The whole idea was to have the internal part of the screw top to be steel, like the inside of the bottle - so there's no plastic touching your liquid. The exterior grip on the lid was always plastic - that's fine. But now, you have to buy the original stainless screw cap, as an accessory, that costs more than 1/3 as much as the entire bottle product. This bottle if great, but now go buy the staibless steel cap for $5.45.
Shame on you Klean Kanteen. 1 star

I purchased one of these for myself after researching the problems with polycarbonate bottles. At the same time I bought SIGG bottles for my kids because they had cool designs on them. Both brands of bottles are great and much safer than the polycarbonates. I like the Klean Kanteen much better than the SIGG for the simple reason that I can put standard ice cubes in it. I have yet to find an ice cube tray that is easy to use that will fit the smaller mouth of the SIGG.

With the Klean Kanteen I get clean water and no taste of metal or plastic or anything other than water. I fill this 27 ounce bottle 3 times during the day to make sure I get enough water. I like the sports cap, because I don't have to take off a cap and lay it down somewhere. I originally bought the bottle with a poly loop cap, but when I am teaching there is never a germ-free spot to set that lid down. So I bought a sport cap, and it is very easy to drink from.

If you buy the 27 ounce Klean Kanteen and like your water cold, I recommend a Built NY 20 oz bottle tote to use with it. The metal becomes VERY cold with ice in the water and with the bottle tote, it stays cold and your hands don't! 5 stars

I just purchased the 40 oz. size. The cap fits well and seals well. The company told me that all the different sizes use the same cap now, so there is no fit problem. The bottle is well finished and strong. Easy to drink from. It is wonderful to be using stainless steel now, and no longer be using Nalgene, which is polycarbonate plastic, and a possible health hazard
(bisphenol A). 5 stars