I read / watched both. They did leave out some important character development and changed the ending but I preferred the anime ending, since the manga was a bit more soul crushing.
And yeah, I grew attached to Daiichi / the older brother the most… followed by that tomboy girl Maki. And even the douchebag characters I hated the most eventually grew on me.
Except Dungbeetle, fuck that guy. Kyubey has nothing on him.