my dad & stepmom gave everyone a klean kanteen bottle for christmas, which i thought was a really great and fun idea. we each got our own colors–i got blue, my husband got green, my sister got pink, and so on. they even found a little kid-sized one for my 4-year-old niece. cute! anyhow, the whole concept was somewhat new to most of the recipients, but my husband and i have been carting around sigg bottles for awhile now. i'm kind of interested to see how they'll compare, now that we have both types in the house. i think the basic difference is that siggs are aluminum and klean kanteens are stainless steel, but there's also the fact that klean kanteens have a much wider neck. have any of you tried both and found a definite preference?