it could have meant that if the "movements" were not similar.
if you zoom in you can see that price moves are almost identical against both currencies. of course exceptions apply in some cases like the middle of the graph (7 Dec) when the price against BTC is dropping much harder than price against USD.
so you have to decide, do you want profit on your BTC or do you want profit on your USD?
Ahhh ..Now it all makes sense. So in that case it would be better to take profits in USD.