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 ha

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.