Do they enjoy dancing with each other as opposed to against each other? It makes no difference.
Each couple will be watching the others on the lookout for who's got the best part of the choreography, who's got better steps, who is dancing front and centre. It's still a power struggle even when there's no title at stake!
Remeber Erin exploding at Brendand when he decided he'd come in the middle out of place during the Vienese Waltz? That was huge no-no in her book, since the nearer the end you dance, the more likely the audience are to remember you? No-one likes dancing-on first.
Professionals as they are though, they make it look like they are enjoying it!