The power rating you have there is - max constant output e.g. if it were in a plane at constant revs. The power in a car fluctuates so much it is hard to give a max rating.
As far as the comparison to the neu you mentioned I would only guess the medusa would would be the better choice
In my 820mm mono boat I do my Medusa 3680-1600KV over 2KW power which draws 120A from 6S 6.8Ah 30C LiPo at straight speed runs. Certainly it's water cooled.
I don't have a 1515 to compare against, but I was running a 2000kv 80mm Medusa in my XT8 truggy on 5s, but recently switched to a Tekin 1700kv truggy motor (2000kv was too fast and couldn't gear down any lower). Power output is about the same but the Medusa did seem a little stronger. Then again, I didn't change gearing, so the lower kv of the Tekin is drawing less current.