Hard to say, a while ago there was some talk about it and I can't remember the specifics, I think Warren claimed that T6 had some component in it that led to their spool valves failing...but other companies don't claim this.
@bismic probably remembers better than I can lol
If it were me, I wouldn't be shopping from someone who is so strict about their warranties. If a company can't make a product that can be used by the majority of the population, they shouldn't advertise it like it's high quality. My opinion though, they are solid injectors from seeing what pops up on here. I haven't seen a post about warren injectors failing, I'm sure other people can agree with that.