If you apply for the TRV before your PR application, if it is refused, you will have to indicate that on form IMM 5669, which asks if you've ever been refused any kind of visa to Canada before? Personally I think this is a red flag question, as are the rest of the questions on IMM 5669, ideally an applicant should answer NO to all those questions to prevent any delays, whether major or minor. However, in hindsight, it's not a really big deal if you have to indicate YES to that question if you explain that your wife is simply trying to visit.
If you apply for the TRV after the PR application, if its refused, you won't have to update any forms or change anything.
It's my opinion that applying for TRV after PR application is way better, despite what others think, because if you're a girlfriend/boyfriend or fiance, your TRV might be more easily refused since they will think you're going to marry in Canada and apply inland, which is almost like a permanent stay visa.
My wife is living proof that its definitely possible to get a TRV after PR application.