I had the same choice several years ago. I was switching between the Beomaster 6500 and the Beolab 200 (the versions with powerlink connections for Beolab Penta mk2 and mk3 are called Beolab 200).
i think there isn’t a better sounding amplifier, but they are just sounding different. I really liked the sound of the Beomaster 6500. Later i mounted the Beolabs 200 back when i switched to newer devices (now connected with Beoconnect core).
Try and decide what you prefer. They are both good amplifiers.