Both bottles are very light and look good. The Sigg is lighter, but not so much to really matter. Sigg wins easily in the looks department with different artwork to choose from and the bottle I have has a nice textured powder coat finish compared to the KK basic look and smooth surface.

Sigg uses an epoxy to protect your water from the aluminum and tells you not to use the bottle for long term storage. Could be a bit worrisome not knowing what’s in the epoxy and the possibility of aluminum contamination. I have not noticed a metallic taste from either bottle drinking straight unfiltered tap water. I prefer the stainless steel of the KK just because it’s probably on the safer side.

The bottles are both lightweight and made of thin metal. I haven’t dented either but I have been very careful with them. Both feel like they would dent quite easily. I have not scratched either bottle and the paint on both looks like new after daily use from work to the gym.

The KK bottle has the cap threading formed into the neck of the bottle while the Sigg uses a metal ring insert in the top of the bottle to thread the cap onto. Some people have complained that the Sigg’s threaded insert is sharp, but I have not had this problem. The KK is more comfortable to drink from though. Also the wide mouth of the bottle makes it easy to put ice cubes in, which you can’t do with the Sigg unless you have very small ice cubes.

I have the loop cap on both bottles. The Sigg I really have to twist the cap on tight so it doesn’t leak. The KK cap seals quite easily and has never leaked. The KK also uses a thicker thread size and is easier to screw the cap onto because of this.

Some people are complaining about sweating. On a hot day with the bottles filled with ice cubes both will sweat, but plastic bottles will also.

If I was going to spend that much money on a water bottle again, I would go with Klean Kanteen without a second thought. The only advantage of the Siggs is the exterior design.

Update Dec 09: Over a year of use now and I have stopped using the Sigg due to their older bottles do in fact have BPA. Something they said it didn’t have, so I won’t buy another bottle from them again since it appears they were lying before. They will replace the older bottles, but you have to pay shipping.

I have 2 Klean Kanteens and both have held up well. Some minor scratches and dents, but still look quite good.

In early 2010, I decided to spring for a second bottle — smaller this time, and with a nice painted color finish (not available when I got my first KK in 2005). Immediately upon receiving it, I could tell something was different. It felt thinner — cheaper. Sure enough, I could squeeze the neck of the bottle and “squish” in the sides. I tried this with my original bottle. No way! It wasn’t budging. I added water and, wow! The water had a terrible metallic taste. I never had this with the original bottle. I washed them both and filled them both from the same water source at the same time. Yup — metallic taste from the 2010 bottle. No taste from the 2005 bottle. I started to wonder if the materials were the same, so I grabbed a small but powerful refrigerator magnet and tried to stick it to the side of each bottle. Remember, Klean Kanteen claims that the bottles are made of “304 stainless steel which has a low nickel content.” (To be exact, 304 Stainless has between 8{660353129f8d892044c993645a1c75194301fec6786a7f617c15adde0b0011e9} and 11{660353129f8d892044c993645a1c75194301fec6786a7f617c15adde0b0011e9} nickel.)

Anyway, anyone with any knowledge of metallurgy knows that a magnet should not stick to 304 stainless steel. And, as expected the magnet does not stick at all to the circa 2005 bottle. But the 2010 bottle, even with the paint on it? The magnetic latched right on, even with the the bottle was turned upside down!

So, this and the metallic taste and the cheap construction leads me to believe that Klean Kanteen is NOT using the materials (304 stainless steel) they claim to use in these bottles. This is a serious accusation and not one I take lightly. But it is a serious concern. KK stakes their claim on providing high quality stainless steel. If they are using another material, they are deceivcing the public by not disclosing this fact.