At some point I want to make a F4T5 preheat fixture and I need your opinions on the ballast, I'm gonna use a Robertson SP48 ballast. There are two listings I'm looking at. A brand new one made in China for 24.95 or a USA made one used with some scuffs for $12.99.

I would say get the used one. Obviously chokes do fail, but not very often. I think a used one will work okay. And it is made in the USA which is nice. Obviously if it is untested you are taking a gamble, but I am assuming you know it works.

Chokes mostly fail as result of stuck starers, but an F4T5 have so low arc voltage that i doubt the stuck starter current would differ much from normal operation current with an F4T5 anyway

Chokes last a long time so new or used, you'll get long life from whatever you choose. Get whatever is preferable to you. The new Chinese-made one does sound nicer because you don't know how many hours the used one might have on it.

I also came across a listing for a Robertson L48 ballast. The seller claims it is new. I'm not sure if it is made in the USA or not, but from what I've seen, the Chinese-made Robertson chokes have a painted finish and say they are made in China on the main label. This one is unfinished and does not say it is Chinese made on the label. Is it actually made in the USA? Also, is it new? It does have some scuff marks on it.

https://ebay.us/m/adDftI