Clucky14.... the discussion on 3dt vs 5dt seems to be evenly split from everything I've read on here, as well as what FSs, nurses and scientists have said to me. There seems to be as many successes at 3dt as with 5dt, so I don't think there's a magic formula.
Some people say that that the best place for an embryo is back inside the body where it's meant to be. That made sense to me, until I read things which said that at 3 days normally the embryo would still be on it's journey, as apparently it doesn't get to the uterus until about day 5, hence why others say that day 5 is the way to go. One of the scientists at the Next G lab told me that it makes no difference at all, and it's more to do with what you're comfortable with, e.g. I liked the idea of having DH's baby inside of me even if it was only 3 days old and didn't take. That's what happened, and strangely I'm kind of at peace knowing that I did have his baby inside of me - so it can be emotionally good too that way. However I think if you have more than one embryo, it makes sense to wait til day 5 to see which one is doing the best.
Not very helpful, as there seems to be many pros and cons!! Each person needs to do what they feel is right for them at that time.