Cambodia seems a lot emptier than Lao. There's a lot culture and heritage sites, but in between there's not much to see (compared to Lao). Still it's incredible how friendly the Khmer people are if you know about their history, especially the Khmer Rouge.
Ankor is totally worth a visit, it's the temples of Indiana Jones and Serious Sam in real life!
The food in cambodia is very tasty, my favorite cambodian dishes are tofu Laab and Khao Lam.