The "Nitro" branding is given to the top-line Sapphire cards. The "SWFT" branding is given to the lower-line XFX cards (their top-line cards are called "MERC"). The SWFT line competes with the Sapphire Pulse models.
Having said that, the differences between them will be insignificant. There might be a slightly stronger factory OC with the Nitro but you'd be looking at no more than a 5% difference in performance. They're both gigantic triple-fan cards which means that they'll both be cool and quiet.
I'm willing to bet that the XFX SWFT is a good deal cheaper than the Sapphire Nitro and if that is the case, get the XFX SWFT.
I've used many different brands of Radeon (and GeForce for that matter) and they all work pretty much the same:
Albatron GeForce FX-5200
XFX GeForce 6200
Palit GeForce 8500 GT 1GB
XFX Radeon HD 4870 (2 cards)
Gigabyte Radeon HD 7970 Windforce (2 cards)
Sapphire Radeon R9 Fury Nitro (2 cards)
XFX Radeon RX 5700 XT THICC-III
Current: OG ATi Radeon RX 6800 XT (Reference Model)
I miss Crossfire.... Anwyay, yeah, get whichever is cheaper and enjoy it! 😀