Some good reading - Dan at The Shrine of the Holy Whapping has a series going on "Purchasing a Parish Hymnal".
Part I asks the key questions, like "Do we really need to SEE the readings as well as HEAR them?" "What styles of music are involved?" "How much money can we dish out?", etc.
Part II describes many of the hymnals individually.
Part III, once it is posted, will cover "the decision". Stay tuned.