Everyone has some great recommendations here. The Hanover St. Chophouse is very fancy (res. req.) and very delicious.

And I HAVE to give love to my favorite homestyle Chinese/blend restaurant in Manchester- Golden Tao on Amory Street. The location is very quaint (inside of a relatively dead plaza) mind you, but don’t let looks fool you. Dine at the restaurant (vs takeout) the food is fresh, the place is always so clean, and the owner is such a sweet woman.

Nashua is smaller, more sparse. Still has a city feel in some areas, but it doesn’t bustle with the quite the same life as Manchester does. Manch has a lot of college-aged/young adult folk who enjoy going out. Downtown can be pretty lively. Tons of restaurants/bars. You’ve got the arena there, too, where many events (concerts, graduations) are held. The city’s board does a good job keeping city events happening as well (food-themed events/local business promotion/etc.) If you are between these two and looking for fun, I’d say Manchester. You’d be close to work, and within two hours either direction you could be in Boston for a night out or on a hike in the mountains.