I beg to disagree - a little anyway.
I think it's BOTH! But I agree in that the entertainer part is the MAJORITY part that "makes it", ie., the show, the evening, the concert, the TV appearance, the dance floor hall, etc. As long as a person has good chops and a good personality and knows how to woo an audience he or she has won 95% of the battle. Having an instrument that sounds reasonably better than a Duck quacking when you press the Keys is the other 5% IMHO. Being an expert player on a $100 Casio Keyboard may still enthrall an audience (most likely not because of the $100 Casio though) but being an expert player on a Korg Pa1X Pro, etc., would enthrall them even more by the simple fact that people like great "sounding" music not just a pretty face. People aren't dumb. They know what a Trombone sounds like from their exposure to music over their lifetime. If the $100 Casio doesn't have a 'convincing' Trombone people will realize it right off the bat and FYI may not come back to hear your stint again because of it -[plus all the other sub-par voices the Keyboard may produce]. Repeat customers are essential in the equation of continuing to prosper and make money in the Gigging arena. To have a Keyboard that has instrument sounds that are "authentic" and life like will only go in furthering your career as a Gigging Keyboardist. That's not to say a $100 Casio won't make you money but a better sounding instrument (Keyboard) will enhance your ability to make MORE imo.

Best regards,
Mike