Wrong, it does make a difference if you are wishing to switch esters. Going from Prop to Sustanon for example. A very fast acting to a very slow acting. Although there are 4 esters in sustanon, the majority of them although released relatively quickly after injection take a time to build up in the system and are released at a slower rate. Going from enanthate to cypionate or vice versa shouldnt be a problem as both esters are almost identical in release pattern.