Some say that DGQB was powerful and the best because his techniques were powerful like DG9J. Some say Xiao Feng was powerful and the best because he could win using basic techniques like Founder's Fist and win. Which is a more better indicator of true strength and power?
False dichotomy really.
Whatever is your strongest is your strongest. If you don't use your strongest and still win that just means your opponent is inferior. That example only shows XF is powerful because he could overcome people without using his full power for instance.
Did Xiao Feng use Founder's Fists against his father, Murong Bo, Murong Fu, You Tanzhi and Xuanci?
I don't know.
Was Xiang Long 28 Zhang inferior or superior to the Shaolin arts that MRB and XYS learned?
Hmmm, IF instead of Demon Subduing Palm and 28 Dragon Palms, IF Jin Yong kept all of Xiao Feng's feats and descriptions identical but just gave him Buddha Palms and Tendon Changing Classic and Marrow Washing Classic and 9 Yang and 'Insert fanciest name' here martial arts, would the 'XF<GJ crowd' immediately rate him much higher?