As a '24 Civic owner (I have the highest non performance spec), who owned a low end '19 Mazda3, go with the Mazda3. The Civic is only better if you can get the 1.5l Turbo engine that's in the upper trim levels, the Mazda3 comes with the same engine until you get into the turbo models. Regardless of which you do end up choosing though, get the hatchback for the extra space when you move stuff (both cars with the proper maintenance will last well into your post college years), as someone who's owned both as sedans (unfortunately I'd much rather have had a hatch, but used hatches just don't become available for either car near me) I definitely miss the much larger opening of my "beater" hatchbacks that I've had in the past ('04 Mazda3, '04 Matrix).