Vile/James/Ike

Reason I think Rabbit values acts of service the most is because:

His prideful ass probably likes to feel pampered, so he likes receiving it. 

He probably very selectively displays it himself, so if you're receiving acts of service from him, it means he values you immensely. Prime example from the show being the multiple times he's organized celebrations for Lucy pre-emptively (believing in her completely that she will have succeeded in whatever she was doing), and also (something I think is very sweet) literally making her Cinderella dress when he thought she had gotten the part for the school play.

Fox on the other hand, it might be me reading too deep into things, but I think he's touch starved. I mean, there's no indication that he was close to anyone aside from his mother, who is now dead. Wolf seems to be the only person he's allowed himself to get close to and, well, it's almost ridiculous how many times this Fox has either admitted he likes being held by Wolf, or has gone out of his way to touch/cuddle him. 

Also, while Rabbit I think is more balanced, Fox is absolutely terrible at gift giving (bro has all he needs due to his wealth so there is no need for gifts, and he's probably really bad at gift giving in general), words of affirmation, and acts of service. That's not to say he's incapable or doesn't do these things, it's just not his go-to-method, so to speak.