I recommend keeping both cards and to test them if they both function well overtime. I heard that many people were having issues with the new XT cards from AMD so for now keep them both to see if any runs into issues.
If you're confident enough that they both work then I would rather sell the Gigabyte because IMO it's aesthetically better and it appears to have a bit of higher boost clock than the Gigabyte
Gigabyte = 2310Mhz
Sapphire = 2360Mhz
Also the Sapphire seems to have more features and having a better cooler than the Gig idk it looks like it.