I don't know much about the 1915s, but finding the 1914s in EX or better can be tough. Especially when u're on a budget
Here are my 1914 CJ federal leaguers - 8 in all. I don't think they are any easier or tougher than the rest of the set, but I haven't exactly kept track either. Nor do I know anything about PSA 8 or better. I don't think I own any PSA 8 or better cards.
Good luck in your quest, Bruce.
Rob