I actually prefer to board last. With the exception of domestic, where grabbing overhead space is essential, I always wait until everyone else has boarded before boarding myself. Why'd I want to be sat down for longer than I need to be?

As for WT+ vs WT - there is of course the advantage of earlier disembarkation, which can be handy when arriving in the USA.

That said, I'd sooner be in WT than WT+ (when I'm not able to fly CW!) as at least there's a good chance of bagging an entire row and being able to stretch out.