I can't speak for Kohler engines, but I hear good things about them.
I do have 2 Honda generators (EU6500iSA and EU2000iA) and a honda mower. Both generaotrs have about 50hrs in year+ I've owned them. Both have exceeded my expectations. Great fuel economy, quiet, and start easily even in single digit temperatures (the pull start and manual choke on the 2k takes a few tries after its been sitting for a few weeks).
The mower (don't know how old) has never required any maintance. I check the oil in the spring. Have only needed add twice in the 6 years I've been using it. Its been put in the garage in the fall with what ever gas is left and no stable or any winterization. Starts right up every spring.
Good luck.