It depends on what would you do with phone.
If yes -> you must study how etc. But you can flash other ROM (better or faster than stock) or kernel(for example undervolt or overclock CPU & GPU). Another interesting thing is Xposed framework (for example transparent status bar and a lot of other)
Next think is so much better backup
But waranty is waranty
Samsung Galaxy SIII
Omega ROM (4.3) v59; Boeffla kernel 5.3; TWRP recovery; Nova launcher Prime; S5 theme; Xposed
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