Isak, easily. Our other options complement him well. Isak, Saka, Havertz, Martinelli, Trossard is a big improvement.
Sesko would be in danger of ending up in a selection no-man's-land. Isak would play (and get injured, but that's another story).
City are about to get sanctioned and quite likely go into transition, Liverpool are maybe losing Salah and Trent, the rest of our squad is peaking and starting to get tapped up. There's well above average major trophy and player retention upside built into a couple of "capstone" signings.