There's no way of doing that. The professional bodies don't keep a record of success rate. In any event it really does r tell you anything as losses can arise for any reason. A deer of authority against you, an unreasonable client who won't compromise, a biased tribunal etc.
It's usually possible to check experience online form a persons profile on the internet but that is usually composed by the barrister themselves.
Not about success rate.
Gradings of prosecutors is just about experience not success rate.
Success rate isn't a measure of how good somebody is. An argument can fail, and usually does, for reasons other than the advocate.