I'm definitely more optimistic about Helion. It's the one that would really dramatically change the economics of power generation at scale, and they seem to have substantially engineered around major challenges like not requiring ignition and minimizing losses to Bremsstrahlung radiation. I like that they're laser-focused on launching and delivering commercial value, even if that means a bit less transparency and less focus on research demonstrations than many would prefer.
If Helion delivers Orion on anywhere close to the target timeline, it seems like they'd be primed to kick off mass production and start shipping units all over the country with minimal regulatory hurdles. With sufficiently high productive capacity, it would effectively make all other forms of power generation obsolete at utility scale. Solar would still great for small/decentralized use cases, but there wouldn't be as much reason for a power company to build new solar plants if they had the option to fill the same real estate with a bunch of Helion machines.
That being said, I'm not not optimistic about steam-based fusion power. It would be less revolutionary, but from what I understand would still be a huge advancement. My read is that it would effectively obsolete fission power and plausibly fossil fuel power as well, if not also grid-scale renewables. It would be like having SMRs with higher efficiency and no major proliferation or meltdown concerns that amplify costs. High neutron output and steam conversion add costs and complexity, but if CFS panned out and Helion didn't, I'd hardly turn my nose at that.
I could also see a world where multiple forms of fusion power pan out, and it turns out to be economical for Helion to sell tritium to other vendors like CFS rather than storing it for 12 years until it decays to He3. Maybe we'd even have colocated plants in a certain ratio where Helion provides on-site tritium generation in the exact volume needed for a D-T reactor.