What's "Fan Foam, HDD 2U" + Very High vs. High Performance Fan

Hello,

Configuring an R7525 I have the option to choose between High Performance Fan x6 and for 100$ more, Very High Performance Fan x6. Is there any disadvantage of picking the very high performance ones?

By the other hand, “Fan Foam, HDD 2U” is optional in HPF and mandatory in VHPF, I think I never seen this fan foam, what it is?