Do you mean to buy or to use for your cat?
Assuming you mean the stud service it depends on a variety of things.
The colours you want out of your litter is one factor. If you have a brown spotty queen and you only want brown spotties then it's no good taking her to a stud that is known to carry snow or marble.
Distance is a factor - don't use a stud too far away from your home because the girl is likely to go off call.
Yes, I think pedigree is important too. And that he's been working as a stud for some time so is 'proven'.
Finally when you choose your stud make sure that the stud owner has a 'free repeat matings' written in her stud agreement. There are STILL people taking money for their stud service when the stud does not sire kittens.
