In my experience, it is more typical to use percent change or relative change in the physical sciences and this is how I was taught. Just to be clear, if you have values t1 and t2, the relative change is (t1-t2)/t1. There is a 1 to 1 correspondence with what you described which is t2/t1.

I think teej explained it well. If I say "the new value is +20% or -20%", it is immediately obvious those have the same magnitude and opposite direction. But, for some people, when I say "the new value is 120% or 80% of the old value", it is not immediately obvious that they have the same magnitude. It requires a small extra step for the reader to realize that this means the same amount of relative change.