Yes, I imagine the optical drives can eat a good amount of power as they spin up.
Assuming the Xbox 360 S transformer is able to output 135W, it would have to draw 145W if you assumed 94% efficiency, which is probably high. It's probably between 80 and 90%. In any case, your 360S is not going to draw 145W from the wall, at any point, period.
Like Al said, the Wii uses about 20W during gameplay, and the output on the supply is rated at 40W or something like that.
Edit:
Another thing to consider is that they're not designing these supplies. They're just rebranded off-the-shelf supplies. They're likely to look at quite a few supplies with different ratings depending on what's available. They may end up with one that has a ton of headroom, if it is abundant, cheap and of good quality.
Assuming the Xbox 360 S transformer is able to output 135W, it would have to draw 145W if you assumed 94% efficiency, which is probably high. It's probably between 80 and 90%. In any case, your 360S is not going to draw 145W from the wall, at any point, period.
Like Al said, the Wii uses about 20W during gameplay, and the output on the supply is rated at 40W or something like that.
Edit:
Another thing to consider is that they're not designing these supplies. They're just rebranded off-the-shelf supplies. They're likely to look at quite a few supplies with different ratings depending on what's available. They may end up with one that has a ton of headroom, if it is abundant, cheap and of good quality.