The old one was better in certain ways, especially how it did not hold back the violence (the Enzyme battle... what a contrast) - Guyver is about violence. Humanity's identity in any form is shaped by violence. Not just the human race, but all forms of life on Earth were created for this purpose; and our freedom was gained when our creators wanted to see whether we could be made even better at violence, and we turned out to be too good at it! Warfare appears to be the rule in this universe, with conflict stretching across hundreds of millions of years. Not to mention how people's inner self, or what they believe it to be, is violated, bent and hammered to violence. Sho, an ordinary kid, is turned into the deadliest thing in the world, perhaps the universe.
Mizuki and her brother - and Natsuki - being the obvious exceptions. If Mizuki ever uses force, even to defend herself, it will truly be a milestone moment.
Natsuki being a Christian, I wish I knew more about Japanese Christianity. I suspect it has a lot in common with Buddhism.
Anyway... the old series better in certain ways, but obviously the new one being superior in others. The animation, for one. And while it takes liberties with the manga timeline, it evidently improves the story and allows for more character development.
The original...
The remake.