IMHO, AILA membership is imperative. Some attorneys are big names, due to their publications, website exposure, or firm size, but this is not always indicative that they are significantly better than a less know attorney. I have also seen experienced, extremely competent, attorneys get so busy that they do not spend the time necessary to properly handle cases. Larger, established firms have much greater overhead expenditures and therefore must charge higher fees. On the other hand, small attorneys who work from their home frequently do not have the resources to properly handle cases and sometimes do not have the experience either. The can, however, charge much lower fees due to much lower overhead and also may be more focussed on a particular case.
For an established firm with high overhead to compete with the small solos, they need to pay employees less or operate on high volume, which usually means that attorneys take less of a role with each case and most case processing, and client questions whenever possible, are handled by paralegals.
Joe makes a good point. I was an immigration attorney for years and new nothing of representing clients in immigration court, asylum, NACARA, TPS, . . . I was only handling business immigration cases. Then, about 3 years ago, I started handling immigration court and other similar matters.
BTW, I recently had an article published in the Winter ABA newsletter, which can be seen at:
http://meetings.abanet.org/webupload/commupload/IC925000/newsletterpubs/immigrationWinter2006.PDF