I kinda like the look of the Y-wing at the moment. OK it isn't going to be able to go against TIE fighters (or Interceptors, or Advanced) but it's a straight up bomber so it shouldn't have to. The Y-wing needs those X-wings or A-wings for interceptions if there are enemy starfighters about. The B-wing, for me, is much more of a multirole heavy fighter. It can hold it's own against TIE fighters and be a real threat to enemy ships but this comes at the expense of mobility.
I can see myself experimenting with all of the Rebel snubfighters at some point or other but I'm leaning towards X-wings and Y-wings at the moment. I have a real soft spot for the A-wing as well so I'm going to try to get a few of them in my list as well.