@VirtualMac2009 - Hi, I feel that both pieces of software are very good, and it comes down to whatever works best for you. It's just that, over time, I started having a few issues with Parallels that made me make the switch to Fusion:
1. Parallels 14 had just being released, so I gave the trial a go, but was unimpressed with the way Parallels popped up an advert every time you started, or resumed, a VM during the trial period. The Fusion trial has been far more unobtrusive in this respect.
2. In the past, I always felt Parallels VMs were much snappier than Fusion ones. However, bugs had started creeping into my Parallels VMs over time, and then I found this guide which greatly helped to speed up my Fusion VMs. So much so, that I don't notice a speed difference between Fusion & Parallels now.
3. I also felt I should reward good business practices, like letting you install Fusion on any machine that you own. Parallels, on the other hand, is restricted to a single machine (I think).
4. Various other little things, like being able to use a keyboard shortcut to enter, and exit, Unity mode in Fusion (I spend a lot of time in Unity). Although though were keyboard shortcuts for Coherence in Parallels - I could never get them to work - and found only the menu bar item worked for me.
So, as I said at the beginning - we're lucky to have two excellent virtualization solutions on macOS for home users. In the end, it came down to the fact that Fusion (and its features) were a better fit for me, (and I was no longer concerned about the speed differences between the two pieces of software).