Egg transfer - day 2 to day 5 - when is best?



I know egg transfer can be any time from day 2 to 5 but I have heard that day 5 blastocyst have the best chance. Is the transfer date recommended by the clinic, or my choice? In the event that they suggested day 2 - why would they do this given blasto is best day, or is it?

I might be wrong so any guidance / feedback would be welcomed!

Thank you xx