High VS Low Power Guitar Speakers G12-65 vs Greenback

What's preferable: Playing loud trough a high powered speaker or playing low through a low powered speaker? I'm playing a Cranked 50W Marshall JCM800 first through a G12-65 and then through a 25W Greenback, but in the case of the Greenback I need too use an attenuator. So, which alternative does sound best to you? My comments at the end of the clip. In the clip below I compare these 2 speaker in 4x12 cabinets instead:    • 70s Vs 80s AC/DC Marshall Cabs Comparison!