Apple are in the process of reducing a developers ability to introduce kexts (kernel extensions) onto your device. They are doing this because software houses that rely on kexts have as a rule proven more than capable of producing sub optimal systems capable of destabilising a Mac. Both VMware and Parallels use kexts; both companies products are easily capable of destabilising a Mac and both companies produce sub optimal software. I have used both VMWare (Fusion) and Parallels on a Mac; out of the two I found Fusion to be the most stable.
CPU usage across both products? Well, Windows if you leave it to 'idle' has a nasty habit of updating. So that's going to bugger up any preconceived ideas of which system is the most efficient. I've seen some 'framework' virtualisation applications cropping up and I have to say slim is best; when they weigh in at around 20mb instead of nearly half a gig, I think that speaks for itself. Veertu Desktop was the first to come onto the App Store and weighed 13MB. Parallels Desktop "Lite" is 234MB?!? Why? Veertu Desktop was a little crude, but it ran like Usain Bolt with NO evidence of ANY hypervisor instabilities. It's a real shame they didn't finish the job off.
The hypervisor framework (released in Yosemite, around 3 years ago), will enable software suppliers to get virtualisation products into the Mac App Store. The framework is not for developers, it is a mechanism to be used by developers to get you the products you want. There are quite a number of free products now appearing that support this framework. As a developer I cannot wait to see more virtualisation products to come out that I can run Windows on (for software development). I look forward to kext free virtualisation. The compromise is likely to be a reduction or removal of gimmickry that burdens the host system. So, no fancy window skins; who's interested in that anyway? No 'side by side' (the hidden windows desktop); again not interested I always run in a window or full screen. No accelerated gaming, though I'm not sure on that one. But, if you seek a gaming machine go native or build one. I seek stable, optimised, fast and efficient virtualisation. Currently neither VMWare or Parallels supply this.
I was considering trying out Parallels Desktop Lite; but if it's bug free and works, why do I need a £60 per yer subscription? By European law, if the product is buggy I'm entitled to a fix; I shouldn't have to pay for it. I'm not keen on companies whose business model is to bind me into a subscription because they're providing me with buggy bloated software.
(@basil) update: this is parallels lite running high sierra