The only real advantage I see to the T444e is that it is a shorter engine. This means that in a dog-nose bus you won't have a doghouse to the right of your feet. This fact made it easy for me to add a passenger seat next to the driver's seat while allowing a reasonable amount of room to enter the stock door of my Thomas/International.
The DT466/DT466e is a stronger puller operating at lower RPM with more torque.
EDIT: Oh, the other big advantage is that it's real easy to find parts for the T444e since the 7.3l Powerstroke is based on the same block. This can make your life a bit easier if you break down out on the road.
I'd prefer a DT466 any day. Sure the T444's are fine engines and all that, but the 466 will outrun it on a hill and with the correct gearing will cruise 75+ all day (as long as they aren't pulling *Too* much weight). They are considered very reliable engines.