Having used all 3 fairly extensively, here are my thoughts on the 3 different pieces of software for what it's worth.
I came from both Romplur & Maize before transitioning to HISE. They are easy to use but you hit issues and/or limitations pretty quickly IMO.
Maize & Romplur are very similar to each other despite the Romplur CEO saying otherwise.
Romplur has a huge issue if you want to use real sample mapping for each individual note and will just grind your DAW to a halt if you have even a modest number of presets/banks.
Maize doesn't have that issue at all depsite being the significantly older software.
With both, you are limited to the built in effects and functionality so if you have far reaching or even moderate ambitions you will hit the ceiling fairly quickly.
They only really have 2 advantages over HISE and one was mentioned by the OP - that you can export both Windows & Mac format plugins on 1 platform, you don't need to have a Mac to export Mac plugins and so on.
The other advantage is ease of install.
Other than that, I would say HISE wins hands down in every other category.
But in fairness to HISE, once you have got your head around the HISE install/build process & how it works, it's not really an issue tbh
After making the move to HISE I would 100% never consider moving back to either of the other 2 and the more I learn with HISE, the more possibilities there are and the more powerful/flexible it becomes.