The Galaxy S21 is much better suited for mobile photography than the Galaxy A71, even though the latter has an additional sensor. This is obviously a case of ‘less is more‘ and Galaxy S21 owners will have a superior camera experience with the triple main camera.
The same goes for the 10MP selfie sensor. The latter may not have a resolution of 32MP but it boasts Dual Pixel autofocus and other advantages that will lead to better results.
The Galaxy A71 was a great phone when it came out and it still is a decent mid-range device, but one of its biggest shortcomings is the lack of any kind of dust and water resistance.
In contrast, the Galaxy S21 has an IP68 rating, which means it can survive after being submerged in up to 1.5m of water for 30 minutes. Practicality aside, the Galaxy S21 has a modernized design and it’s arguably a better looking phone.