[Newbies] DIfferent OS X VMs

Can someone explain the differences between the two branches of VM on offer at ftp://ftp.squeak.org/current_stable/mac/ ?

I understand that the 3.8 (yellow icon) branch is based on John McIntosh's work found at http://www.smalltalkconsulting.com/squeak.html and that the 3.9 (blue icon) branch appears to be Ian Piumarta's work from http://www.squeakvm.org/unix/ , but I can't find any information as to which VM should be preferred and for what reasons.

Well, I do know that the new (great!) true-type font integration requires John's VM, but I wonder are there any other key differences?

Thanks, Michael