I think very carefully when buying a yoyo and it’s string type like some people like 100% cotton with type 8.Or even the dye if your a public preformer.
String is so easily changed out that it is the least consideration when buying a yoyo. Most people have a stock of their favorite string on hand. If you don’t you should. Relying on the single string that comes w/a new yoyo is not practical. It will only last a couple of days usually.