For me, one of the biggest arguments in favour of the SLI/IEE typing for Zoe and Wash is that they both get along much better with Mal than with Jayne. In fact, Mal, Zoe, and Wash kind of form the "core" of the crew. It would make sense if they were members of Mal's quadra, not Jayne's.
LSI/EIE is still my backup typing, though.