There are a lot of variables. What sort of coral are you talking about. How much light does it get in the old tank vs. New tank. Both intensity as well as duration.
As a rule most people acclimate corals on the bottom and slowly move them up. I tend to lose small corals on the sand bed. Especially small sps frags. So I either put them on a frag rack, or if I'm doing a wc I tend to epoxy things in right away. Not the best advice to epoxy stuff right away I guess. I always figure once it's there, it will acclimate. Sometimes moving a coral around too much will stress it worse then the initial shock. Sometimes it works, sometimes it doesn't. Under 4 t5s if it's sps I would shoot for the high levels. Intensity can be made up with duration in many instances.