Not OP but I, personally, stopped using Fusion because of the constant annoying advertisements. I could understand if it were free but I paid a non-trivial amount for it out-of-pocket.
I can't complain about Parallels' performance. I was satisfied with it in that regard.
Source on VirtualBox being faster? Couple of benchmarks I've seen put VirtualBox at considerably slower[1] and Fusion slightly to considerably faster than Parallels.