It is of course more important for them to win a Champions League championship for the first time in their history. Guardiola wants to be a part of this historical moment for them too. But making double must also be looking really nice for them. I would love to see them winning the CL title but for the PL one I hope it will be Arsenal.
I think they're performing well in the Champions League. They're confident going into the playoffs after beating some great teams. You're right. They should work hard in the Champions League.
Arsenal are tough, but let's not kid ourselves. In the Premier League, beating Man City will be difficult. However, they haven't held that championship in about 20 years. They've worked hard all year and deserve to win