Sigg:
Pros:
- Thick walled
- Cute designs
- Easy to drink from the narrow top
Cons:
- Difficult to clean - you can buy a special brush to wash it, but you definitely can't wash it by hand
- Heavy - because it's so thick, it is pretty heavy (though you could use it in self-defense)
- Dents easily - for someone like me who drops their waterbottle constantly, this is an issue
- The lid of the bottle can grow mold if it's not cleaned very thoroughly - gross!
- My Sigg started shedding paint/plastic bits at the top, so that was the last straw for me
- Made out of aluminum, which has some questionable health/safety issues (i.e. BPA in the lining)
Klean Kanteen:
Pros:
- Easy to wash - you don't need a special brush to wash it and there are no places where mold can grow
- Wide opening - you can put ice cubes into your waterbottle
- Made out of stainless steel, which is safe for you
- Light and easy to carry
- Seems to dent a lot less - I've dropped mine a few times and no dents yet
Cons:
- Wide opening - I know that I put this in the pros, but I also spill a lot of water while trying to drink out of this
- Few designs and limited colors
- My roommate says that hers leaks, but I haven't had that problem
Tally:
Sigg: +3, -6
Klean Kanteen: +5, -3
And that is why I say that my Klean Kanteen is the winner. I love it!