I was a member for a couple of years (I don't renew my membership anymore though).
The biggest advantage for me was being able to compete in YKC classes and at the Crufts finals which was a fantastic experience
However, not all the competitions are on the weekend days (I found I couldnt go to some of my finals due to college commitments).
The training days/activity weekends I went to were excellent
.
Meg is right...things are a bit different for the over 18's. It would be worth checking the most recent rules to see how it would affect the competitions you are eligible for.
If you do join I hope you enjoy