In class today, we were introduced to 「に比べると」, 「と比べると」, 「に比べて」, and 「と比べって」. My sensei said that the four are essentially about the same and that we needn't worry too much about when to use which, as most Japanese folks don't either.
However, regarding the particles, I believe he kind of said that 「に」 is used when comparing something to something else in a "for example," random-selection kind of way, whereas 「と」 is more used when comparing things like look the same or similar. But perhaps I misunderstood.