Why do I care about Vaughn's fourth home run in advanced-A? Well, it equals his total from 68 games with Savannah, when he hit .286/.405/.408 with 14 doubles and four homers.
Not to read too much into tiny sample sizes, but after an extra base hit in 6.7% of his plate appearanes in Savannah, he's up to 8.5% in St. Lucie.
Minor League park factors are really hard. All of the numbers I've seen have Historic Grayson Stadium in Savannah as a strong pitchers' park. Even so, I think that the number might even understate how hard it is to hit here and how much it helps pitchers by depressing homer and overall hit rate.
Also, homers are good.