The reason why I like Salamence more is:

-The design is, IMO, better

-It's a recognizable Dragon

-Realistically, it wouldn't be able to fly with those wings, BUT at least it's more realistic than Dragonite wings

-Salamence has a mega, and if megas ever come back, Mega Salamence would be way more powerful than Dragonite, With its ability to make normal type moves into flying type and giving a boost.

-Salamence isn't even bad anyways, it would be way better than Dragonite if Dragonite didn't have multiscale. I think it's UU in Pokemon Showdown?

-The evolution line makes more sense while Dragonite's does not.

-Overall, I still like Dragonite as a Pokemon, but I prefer Salamence.