I wouldnt expect too much from any with regard to opportunities albeit perhaps you will need to be more specific regarding the opportunities you have in mind.
The organisations you mention committ most of their resources to fighting ga's corner, as laudable as that is dont expect too much else in return from a personal perspective.
Aopa us so a great deal for indivdual members but aopa uk is a very different beast with a different agenda. Balpa without doubt believe their interests are with the commercial community even if even some of their members would rather balpa had not forgotten the roots of its members and aviation in general.
Some of the other do a good job within their niche and are perhaps more focused on the individual than those already mentioned.