There are many possible answers to this question.
Unfortunately, we can't really help you out all that much if you don't give us more info. First thing is first; is clonazepam the first drug you've tried for anxiety? If so, I very much recommend that you take something else. While Benzodiazepines are some of the most effective drugs in existence for anxiety - they're not sustainable in the long-term (due to tolerance) and a lot of people end up chasing that original, nice and relaxing, anxiolytic feeling. Although, now that I just thought about it - the title implies that you know about benzodiazepines and their risks. Again, they have benefits, especially for quick, sudden, immediate attacks of anxiety (panic attacks being one of them).
Anyways, to get to your real question - all benzo's are effective for anxiety. There really is no "one" benzodiazepines that's the best. There are ones that are more powerful, but more powerful isn't necessarily the best option. For instance, I could choose to be prescribed something much stronger than Ativan (Lorazepam) for anxiety. Probably a high dose of Klonopin or Xanax, however, Ativan (while it the one of the lesser benzos, and only gives me 50% of the anxiolytic effects of Valium or Xanax) I still opt over those for my sudden anxiety due to the fact that it seems to have the least amount of side-effects.
If I have a sudden attack of anxiety during the day - most of the time, I need to be able to get over that anxiety and get back to my life. Any other benzodiazepine would make me too sleepy to work during the day and I would no longer be able to function correctly if I took it. Ativan, while less power and not quite as anxiolytic, kills a lot of my anxiety and still allows me to feel mostly alert and awake. Any other benzo is going to make me look drugged and feel drugged. Especially since I work retail; their's no way I could take something like Xanax at work. I'd get fired instantly.
So all that is something to think about.