Kohler and Delta both make two different quality faucets - simply put they both produce a line "retail" products with lots of plastic parts and a "professional" product line with better quality products that are mostly metal (metal drains, handles, etc.). If you visit your local Kitchen and Bath showroom they will be able to help you sort though that.
Now, all that being said, ALL products by Delta and Kohler (even the less expensive, plastic, ones) have lifetimes warranties. But, the better quality you start with up front means less replacement/warranty issues down the road.
We have clients (homeowners, designers, contractors) that will swear by one or the other, but we haven't seen any major issues with either one. Ultimately, we do recommend the faucets in the "professional line" from either one, then pick the style and finish you like the best :). Good luck with your project, and hopefully that helps!
Q