21 is just more cohesive than 25 and it has a better flow/sequence of the songs i guess.
when i listen to 21, i barely skip any track, rolling in the deep is an amazing opening track, and the transition from turning tables to dont you remember to set fire to the rain is just flawless, it just flows really well for me... and the sound of the songs feel really connected to each other as a whole which makes it a really great album.
25 is cohesive for me in a sense that Hello, When We Were Young and Million Years Ago alone and i'm already sold with the theme, which is more of a quarter-life crisis/nostalgia theme when you're on your mid-20s. Water Under The Bridge, River Lea, Sweetest Devotion and Remedy just expands it a bit further since these are all personal songs.
Love in The Dark, All I Ask, I Miss You and Send My Love adds more variety to the album as it introduces different flavors that people can still relate to being 25-ish. That's why for me it's a better album than 21
and i think 21 is bound to be more cohesive as it focused solely on her heartbreak, whereas in 25, a lot of things can really happen during this time of our lives not just relationship with someone, it's more of looking into life overall, looking back, looking into ourselves and looking ahead.
