I’m from Athens, so i’m a little bit biased I must say. But don’t worry, I’ve done my fair share of partying in Thessaloniki. Both are great, but the vibe is totally different. Athens has more of an artsy and grunge crowd, because of all the university students. There’s also an upscale and touristy crowd, but that’s less fun. Thessaloniki is great, more chill and beachy because of their beach bars and clubs. Athens will give you way more of a city feel, and you won’t feel like you’re in a summer vacation spot.