Scalability can be simply divided into 2 definitions,speed and capacity.
Confirmation speed and decentralization are difficult to achieve at the same time, but capacity and decentralization have successful solutions. For example, DAG.
However, when analyzing scalability and decentralization, you must consider security. The security discussion boundary determines the degree of scalability and decentralization.
So,for bitcoin,I prefer decentralization.That's why it exits.
No decentralization,No Bitcoin!