PSA Advice?

Hey all. I'm sure there are an overwhelming amount of PSA questions on here but here comes another. My bad.....

I'm about to make my first submission to PSA of about 50 cards. Half vintage, half modern.

The problem I'm running into right now is deciding which cards to submit. In a specific scenario, I'm having a hard time deciding between say, a Hank Aaron card that has some corner wear and may not grade so high, or a lesser known Joe Morgan card that looks like it would grade very high? Another example would be my Lou Brock RC. It's in decent shape but is there a world where grading it gives it LESS value were it not to score very high?

Enough rambling. Any advice on the subject would be excellent. Cheers.