I agree BBH, it probably comes down to this:
All in my opinion of course...
I mean, how do we rate the difficulty of an STG? Number of bullets, their accuracy and speed? Enemy density, their aggressiveness, position? Or maybe stage layout? No matter how many points one considers, all of them will remain very relative criteria with their weight on difficulty changing from title to title. You already mentioned save states, there's also the question of auto fire use and other options modern players can access to accelerate their progress and change a once high difficulty game to a standard challenge.
Yet, I'd still consider a Blazing Star clear more difficult, than a Pulstar one, but I agree that the difference in difficulty has levelled over the years. My reasons would be, that Blazing Star has no extends, no speed-up options, only a manual trigger speed increase and overall a more dynamic gameplay, which makes it difficult to play through with memorization alone. After a while, there will be no luck involved in Pulstar, in Blazing Star however, dodging certain bullet patterns will still heavily depend on luck, like at least 60 (luck) to 40 (memory). From my experience, players who have cleared Pulstar, can likely do it again, even after a longer pause. That's not the case with Blazing Star.
Finally, an extreme low-rank play in Blazing Star changes a lot, I agree. But you not only have to let all the extras go, you should time-out bosses, too, which demands quite a bit of practice. It's also a drastic change in game play, up to the point where it's not the same game anymore. But even then, the last parts can get you. Especially the last boss. So, despite your strong arguments, I'd still argue, that even a low rank play makes Blazing Star not easier than Pulstar. It depends how you look at it, though, so of course it's all in my pinion, too
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PS: I remember how Gemant once posted, that very few western players have cleared Blazing Star on one credit, while a lot have cleared Pulstar and that overall the former is more difficult. I'm pretty sure he was referring to a time before save states became available. I could also imagine, that Asian players used auto fire, since it's common there and considered as a valid part of a game.