I'll start with the seasons.
Spring: 3.5/10
The way the homing shots are angled, they're only about as effective as the summer sub shots as far as area coverage goes. That's not to say summer is better in that regard, just that spring and summer are mostly interchangeable as far as their shots go. However, spring's release has very little use in this game, aside from stage 3. Since bullets are rarely going to be sitting still, a one time high area clear is less effective than a long lasting low area clear. The spring release is certainly useful, but there's nowhere in the game where it's more useful than any other release (aside from stage 3). It also has the hardest Okina last spell.
Summer: 9/10
Along with spring, the sub options are the best for clearing stages. The wide area makes things like stage 4 and 5 significantly easier. But the selling point for them is their incredible damage when shotgunning. This is noticeable in certain stage portions, such as the post midboss section of stage 4. The real reason summer is so powerful, though, is the release. The fact that it only consumes 1 option means that, where the other releases are going to stay in the level 3-4 range for most of the game, summer will be stay around level 5-6 allowing you to get more potent piv items. Furthermore, if you can drop a high level release on the boss at the beginning of a pattern and shotgun for a moment, it actually do more damage than winter. Even if you don't care about score (which you should, considering lives are linked to it), summer still has a great balance of range for stages and damage for bosses. The Okina last spell is harder than winter but easier than autumn.
Autumn: 9/10
The autumn sub shots are hand down the worst in the game, providing extremely little extra damage or range. But who uses autumn for the sub shot? The release lasts about as long as mid-level winter and follows you, providing a shield against bullets and allowing you to clear several spots at once. It's the best release for scoring and can make survival a lot easier. It's also the most versatile; any of the playable characters can use autumn effectively for a 1CC, though some are clearly better than others. Its weakness is that it doesn't make you invincible to enemies, and its low area means you have to get veeeery close to enemies. Everyone's had the experience where they're zipping towards the boss and accidentally crash into them, wasting their release. Autumn's Okina pattern is harder than summer but easier than spring.
Winter: 8/10
This subshot is the only one which provides a high damage boost from the bottom of the screen. Something 3/4 of the players desperately need. Unless you're Marisa, it's hands down the best sub option for no release runs, and even if you are Marisa it's still pretty good. Its release is very long lasting, making it good for scoring on boss nonspells. It does have a weakness in that it can't be spammed on stage portions the way summer, autumn, and even spring can. It's really the most well-rounded season, the only reason it's lower than summer and autumn is that it isn't able to cheese many patterns the way they can. Its Okina last spell is the easiest.
Reimu: 8/10
Reimu's ability to aim her homing shots outward or forward surprisingly helps a ton. She has good spread and decent damage. She's the best for no release runs, hands down. However, if you're using releases then she's kind of lack-luster. For any season except spring, there's someone who can use that season more effectively. Her bomb is also extremely ineffective. In the end Reimu is like winter: the most balanced of the players, but unable to cheese anything, putting her below the ones who can.
Cirno: 8.5/10
Cirno's spread is almost about as effective on stages as Reimu's homing, though it's noticeably worse on bosses if you're at the bottom of the screen. When you're shotgunning, though, it does incredible damage. And in a game where you can plant bullet clears in the boss's face every pattern, the opportunities for shotgunning are plenty. Combine this with summer, which further boosts your shotgunning damage and allows you to spam bullet clears while keeping your options, and you can clear several patterns as quickly as Marisa/Winter. Not to mention being able to melt through stages thanks to the double spread. Unfortunately, Cirno is really only good with summer. Her low speed makes autumn ineffective, she doesn't need the range that spring provides, and if you're going for winter you're better off with Reimu, who doesn't have to rely on releases on bosses. That's why, despite Cirno summer being amazing, Cirno as a whole can't get a higher score.
Aya: 7.5/10
Aya, like Cirno, is really good with one season but pretty awful with all the others. Her main shot does abysmal damage in general, and only ok damage when shotgunning. It doesn't even have a good spread. What she does have going for her are a long, powerful, easy to use bomb, and a ridiculous speed which ups both the risk and the reward in autumn's "high risk high reward" style. Aya/Autumn gets resources incredibly quickly, but unfortunately you get nothing for reaching an extend with max lives, so all those resources tend to go to waste. Still, I'd imagine she's the best for score.
Marisa: 8/10
Marisa's main shot is rather bad. It does good damage in the early game, but generally you'll have a hard time getting all four lasers to hit the boss in the later stages. Her damage is still higher than everyone except shotgunning Cirno, even with only 2 or 3 lasers, but it's not enough to make up for her low range on stages. Her bomb also sucks, arguably worse than Reimu's. That said, she's the player able to get the most use out of the most seasons. She has enough damage on her own that spring and summer are viable options, even if you don't like to shotgun with summer. Her speed isn't quite as high as Aya's, but still high enough to get some good use out of autumn. And you'll actually have decent dps with Marisa/Autumn. Finally, while you'd be trading your stage coverage, Marisa/Winter is able to melt through bosses at a ridiculous speed.
