Out of the three towns you're considering, Evanston has easily the biggest and most varied restaurant scene, although it's easy to get to Evanston for those living just north in Wilmette or Winnetka. Downtown Evanston is chock full of restaurants of every description. (There are also excellent restaurants elsewhere in Evanston, particularly along Main Street, Chicago Avenue, and Central Street, but we'll stick to those downtown, in walking distance of either hotel.) Most of the nicer restaurants accept reservations, which are generally advisable, especially on weekends, when waits without a reservation can be lengthy almost anywhere. Many but not all of the restaurants in downtown Evanston are open for lunch as well as dinner.
If you're looking for an upscale dinner with creative cuisine (and it sounds like you are), Quince is excellent and would be my top pick. Chef's Station is very good too and is my second choice. The Stained Glass is good too, and is a bit more casual, as it also serves as a wine bar. Found is a new small-plates restaurant and it's excellent, but they don't accept reservations and if you're not there by 5:30, waits to be seated can horrendous (well over an hour), even on weekdays. Pete Miller's is good if you're looking for a steakhouse, and so are Davis Street Fishmarket and Bistro Bordeaux for what you would guess from their names.

There are some very good ethnic restaurants as well, although many don't take reservations, but waits are not necessarily a problem. Some of the best include Thai Sookdee, Lulu's Dim Sum (pan-Asian), Dixie Kitchen (southern/Cajun), That Little Mexican Café, 527 Café (Taiwanese), Pine Yard (Szechwan/Cantonese), and Mount Everest (Indian/Nepalese). I've had some not-so-great experiences at Tapas Barcelona (poor service) and Koi (often overly sweet) so I'm hesitant to recommend those two.
And for more casual fare, there's a terrific place for burgers and shakes called Edzo's, which is only open for lunch, not dinner. Lou Malnati's serves Chicago-style deep-dish pizza downtown, and so does Giordano's, for double-crust "stuffed" pizza. Prairie Moon is a casual place that combines a sports bar with California cuisine and it's quite good as well.
Unfortunately, two of my absolute favorites in Evanston are not downtown, but are in the vicinity of Chicago and Main, about a mile south of downtown Evanston. Oceanique is an upscale chef-driven restaurant specializing in seafood, and I like it even more than Quince. Campagnola is a casual neighborhood gem, nominally Italian but much of the menu leans towards contemporary American.