In theory the dvd is 3 times as fast...
But in real life, its an optimal situation where it is 3 times as fast.
the drive doesnt just boot up at maximum speed..
When copying a dvd to your xbox with a lot of small files, it could take much longer than copying a dvd of the same size consisting of one or more larger files. Then the dvd can really reach its higher transfer speed but the small files are already finished before the drive can reach its maximum speed so the speed for that file is much lower.
I think u have to calculate the acces time to reach a good estimate for the drive speed, and its always an estimate. If its 3 times faster with loading game A ... chances are its not 3 times faster in game B.
i dont think access time of the 360 dvd rom is 3 times as fast as the xbox dvd.... maybe im wrong here i didnt check it ...
By making good use of caching techniques they could boost up the load times a lot, but that doesnt count when running older games over an emulator.
The harddrive will be a lot faster i presume, so i guess when u load something out of the cache it will load very quickly...
with kind regards
Marco