Chelsea seem to be interested in signing Bellingham and Declan Rice now. But I assume that they will go for signing only one of these players. However these players don't play in the exact same positions actually. Declan Rice is more of a defensive midfielder. But he does a good job when he has a chance in the central midfield also (1 goal in 2 matches as CM).

Bellingham is already a fascinating central midfielder and he is playing attacking focused which would be very useful for Chelsea. He has already got 5 goals and 2 assists in 15 matches. On the other hand, signing Bellingham would be a much more difficult task for Chelsea because they won't be the only team after him surely. We might see Real Madrid joining the race and then Chelsea wouldn't stand much chance to sign him. I guess he wouldn't prefer Chelsea to Real Madrid.