Phillips Arena is smack downtown, adjacent to CNN Center and the Omni Hotel, which is pricey. There's a Super8 which isn't a bad place to stay for economy. The Westin is obv. nice. Have no experience with other hotels.
Be aware there is close to nothing to do downtown after dark. There are a few dining options inside CNN Center, but everything inside the Omni is tourist priced.
Underground Atlanta added some bars and such over the past year or so. You can safely walk or ride the train there from Phillips, if you feel compelled.
How are you getting to Atlanta, and from where?
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