Any external reference like that is not guaranteed to exist when someone reads your review in a month, 6 months or more. Profiles (and reviews) get removed for various reasons.
If you were writing a magazine article, it would be bad practice to write "see page 37 in this issue for comparison." Once material goes internet, page numbers and so on are meaningless. (You would include a complete reference or quote: "ttcttc, in a post to TER on 2/21/2016, asked, "Can you mention other providers in a review of a provider?" That is the issue I address herein.")
There is also the YMMV factor. Your experience with A and B went one way. Someone else might have had a different experience with B and draw a completely different conclusion about A.
A review, IMO, should be a stand alone work that requires minimal cross referencing or checking ... the obvious exceptions being to that Provider's own websites, ads, and reviews.
Posted By: ttcttc
I should know this, as I have written over 100 reviews, but I don't and this seems like the right place to ask.
I am guessing that the answer is no, since no one ever does.
But I just wrote two reviews and in both cases, it would have been perfect to say something like "this provider is like x, only better at BBBJ and taller." Or "the experience with this provider is like being with a Spanish version of x."