The difference is....
The difference between 140 KIAS and 180 KIAS (besides 40 kts)....is, on the old-style RAT, the RAT will not run with the gear down. So, on approach, at 140 KIAS or greater, you drop the gear, and the RAT quits.
Now, when you introduce the scenario of a go-around on ELEC EMER CONFIG....and, for an unrelated reason, you cannot raise the gear, you will not be able to recover the RAT.
Again, this applies to the old style RAT.
However, there's hope on the horizon....
If you run into this problem....a go-around (hoping to recover the RAT function) but the gear is down and cannot be retracted, you can recover the RAT by pulling the LGCIU 1 CB AND flying at a speed at least 180 KIAS. (I've seen figures of 185 KIAS in some publications.)
Of course, this does not apply to the new RAT (which is larger).
Hope this helps....
Fly safe,
PantLoad