Both Rem & Emilia are mostly pvp heroes. Since you are not into pvp atm, you should go for your fav character.

Rem had her time, while Emilia stocks have been consistently high since release. I'd easily go for her over Rem

So, yea basically what Xalgem said. Emilia is better overall for pvp than Rem is now. I'd shoot for Emilia and then if you're feeling ballsy you can use whatever bm's you have left to shoot for Rem. Rem can still F things up pretty hard in the right drafts. Usually, I tell myself and other people to only pull for a hero only if they have 605 bm's but Rem still has some use left and she's limited. 

But ofc ultimately this is a game. Pick w/e char makes you think will make you the happiest.

Rem can solo win. Amazing character.

Rem solo win, Rem for anti hwayoung. 

Emilia is really good in pve if you give her magahara(she is getting million turns and constantly cr pushes allies)

I have both and while Rem is good,her buff have a very long cooldown and her s2 is an rng

Rem over Emilia, but it’s very close. The reason I would go for Rem, she can be used in more teams. Arena and guild war defense, she’s pretty solid.