when a media institution does a poll, it's intended audience is it's readers and so you need to mentally adjust for the various biases. when pew does a poll, the intended audience is....how to say this...washington. "serious people". they consequently have a heightened level of importance.
that doesn't mean they're more right. it just means that the results reflect what a component of the inside wants another component of the inside to think.
trump at 37 is not particular impressive. but, clinton at 41 is surprisingly low.
it's curious to me that pew's results are quite similar to breitbart's, given that this was the poll that breitbart apparently commissioned to "correct the skew".