I have the ETS and my shroud isn't attatched by weld like has been mentioned as a difference between the ets and the su. Mine had 4 bolts that hold the shroud on just like the su appears to have. So as far as an attatchment weld there is no issue on mine.
Only difference between the su and the ets appears to be a polished finish on the sides of the ic itself. The shroud and everything else is the same. So it appears you're pying an extra $35 for a polished side on the ic. Which is all fine if you want ot to be polished. Tho the coldpipe is textured, so the ETS matches the coldpipe better and looks mroe stock than the polished SU.
Unless you pop the hood you'll never notice the difference. If it was an fmic that can be seen from the outside I'd go with a polished look that stands out and looks better. But for the tmic, you never see it so the extra $35 for a polished look wouldnt matter to me.
Also, since the textured ets matches the textured coldpipe, if a cop pulls you over and asks to pop the hood, it would look more stock looking with a testured tmic as opposed to the polished look and he might not even notice that its aftermarket where as the more detail the piece has the more suspiscion the cop might think. That's something else to think about, If they questioned your intercooler you could just say you took the cover off of it, whereas the polished piece would clearly look like an upgraded performance part and you could get a referee ticket for something like that at least here in CA.
sorry for blabbing, but thats my 2 pennies right there, not knocking the su, it looks sweet, but you dont see it from the outside so it wouldnt be worth the extra price for me personally.