if you want longer software support for your phone get the a54 if you want a slightly better camera (mostly better in zoom) go for s21 fe. i can't confirm but i have heard about battery drain issues on s21 fe use the phone heavily after you bu...

S21 is simply better phone. Faster, better cameras, smaller bezels etc. But, if your priority is battery, A54 is better choice.

It's up to you. But the A54 is heavier, 202 grs, whereas s21fe is only 177 grs. But, A54 has 5000mah vs 4500mah for s21fe. Personally, i would choose s21fe.