compat-amd packages

Just wondering, is there a benefit to continue to use compat6x-amd package or should I use an upgraded version, like compat7x or 8x?

Is there an advantage or disadvantage?

I mostly install this package when using vmware.
the software you use dictates the one you need.
The real-time linker is looking for a specific library version.
I don't use compatX libraries, but I assume each library is uniquely named.

It's also not either/or, you can have all the compatX packages installed simultaneously.
These packages are for binary compatibility with older versions of FreeBSD. With these you can, for example, run FreeBSD 8 binaries on FreeBSD 10.

You normally do not need any of them.
They are needed for binary only software where it's not possible to recompile the software for newer versions of FreeBSD for whatever reason, the source code might not be available or it no longer compiles on newer versions of FreeBSD.

Something to note about 32-bit i386 binary only FreeBSD binaries. You're not going to be able to run them on 64-bit amd64 FreeBSD very easily, we don't have any i386 compat packages that you could install on amd64. You're going to need to set up an i386 jail to run that 32-bit binary only software.