Who should go first? Just got Fenrir right after Graymane))
Other leveled blues I have:
5* - Vela
4* - Boril, Kiril, Sonya.
Do you have 6 telescopes? Do you have any other 4 star blues that you haven’t leveled yet?
A thing you’ll hear repeated here frequently is that you get more out of maxing a solid group of 4 stars first before you get too much into 5 stars, since 5 stars require so much in terms of time and resources. Grimm for example would be a good addition to your team.
To answer your question though, I think both will be effective for you but Fenrir might work just a little a bit better.
I almost always use Tiburtus, Grimm is not so different
I want a decent sniper, preferly as 5*, and do not want to level dupe Sonya.