Charlotte or Atlanta?

I would chose based on preference for which city you want to live in as well as considerations specific to your bank and the team you're joining. 

Charlotte is a cleaner and smaller city. There has been a lot of growth and development over the past 10 years and there's a number of nice mixed-use areas with restaurants / apartments / bars / social spaces, however, there is not much a true "city" feel to Charlotte and is more of a commuter city with the "Uptown" business district area fairly quiet outside of business hours. 

Atlanta is a much larger city and much more culturally diverse. Atlanta will attract more entertainment events (whether that be large scale events or small scale like a small band / comedian touring). Atlanta continues to grow and also continues developing new mixed-use areas in a few different neighborhoods. 

From a purely business standpoint, Atlanta is a larger hub city in terms of # of Fortune 500 company HQs, # of regional / satellite offices, and # of national conferences (also has massive international airport). In terms of # of Investment Banks, notionally Atlanta may have a few more when you count # of regional offices for bank's headquartered elsewhere. Charlotte is a banking city but many of these are back-office banking jobs for Bank of America, Wells Fargo, and Truist (with primary IB presence based elsewhere). Charlotte has a decent sized IB / PE presence but notionally Atlanta feels a bit bigger. 

Ultimately, there's not that material of a difference compared to say living in NY where the number of IB / PE jobs increases exponentially. In deciding where to go, I'd first consider where you want to live, then also think about considerations specific to your bank (where is my group head based, where are majority of analysts/associates based, which office has higher headcount, etc.). 

Source: Have lived in and worked in banking in both cities