What happens when two brand new violas are played by two violists with contrasting repertoire?

Following his similar experiment consisting of three cellists playing one cello, Ian McWilliams tests out two of his newly made violas on two professional musicians. 

Violists Andreas Willwohl and Kirstin Maria Pientka trial both McWilliams’s 40.6 cm based on a ‘del Gesù’ violin model and his 41.6 cm da Salo model viola. Willwohl performs the Walton’s viola concerto whilst Pientka performs Bach.