You would be struggling to find an independent review of player performance for that game that gives a higher rating mark to Walker than Trippier.
Walker is probably slightly faster and more physical, but Trippier appears to have better creativity (control, vision, touch etc). I have watched a number of Spurs' games since Walker has been 'rested' towards the end of the season and in each one Trippier has been very impressive, he is also home grown.
I agree Walker appears an improvement on last year's full backs, I just don't think he's worth the sums Spurs seem to be demanding.