I don't get it. How can ANYONE say that SA is harder than UFO? The only way you are going to lose an extra life in SA is if you die five times against attacks that gives life stars. If you die five times in UFO against a boss, you'll have all your power drained and only three lives left at best. And at that point you are off to harvest some more lives... which can fail as well.
SA does things a hell of a lot better in my opinion because you don't need to work for the extra lives. You just need to do well at the bosses i.e not die. In UFO you are gonna have to memorize strategies for UFO summoning and what not. And let's not forget annoying cases in which the red UFO you desperately need will flippantly fly off screen or just into a bullet hell.
Add to that the fact that UFO have absolutely RAPE spellcards as Bananamatic also mentions.
I'd say that pretty much anything Kogasa have is way too hard for a stage 2 boss. The second boss-card being absolutely unacceptable.
Ichirin have the merciless first bosscard which can and will molest you into a world of despair if you don't bomb it or get lucky and everything else she have is also very difficult. Though most Stage 3 bosses have a certain level of difficulty.
Murasa have four spellcards and three non-spells. The non-spells are okay and so are the first and second card but the third one also strikes me as absolute bullshit. If i'm not getting hit by the debris or the bullets that are spawned by the debris i'm hit by the pattern that follows onward. That attack is risk factor major. The final card is not that bad though.
Shou is an evil girl. Her laser non-spells are murderous and her spellcards are all very difficult. I'm not complaing too much about the spells though. They are okay. Aside from Vajra that is. My gripe lies with her non-spells. Aside from the 3rd one which can be quite entertaining, her non-spells are unforgiving bullshit.
Byakuren = Super hard spellcards en masse. Her first one is very difficult and it feels like it behaves differently leading me to the conclusion that its relatively easy 1 of 3 times but the rest you have to be very lucky. Her second is memorization. The third is rather managable. The fourth is easy if we compare it to the MS version but its still a hard card. SC5 is micromemorizable as far as i can see and SC6 is a spellcard i personally think to be harder than VoWG when VoWG doesn't spam walls.
Just put it like this: SA Stage 1, 2 and 3 are a breeze. SA is easier. And much better IMO.
In all honesty, even if you can only play on Easy, do not play IN on Easy. IN Easy has almost nothing onscreen the entire time.
It's very simple to 1cc the game, but you won't get any better. Even though it's difficult, try playing on Normal. You'll improve through IN Normal much faster than you would IN Easy. Easy Mode is meant to warm you up to the rest of the series, and IN's does not do that. The others do! By all means, play Easy on the others, but don't bother with IN Easy.
I remember beating IN easy when i first touched the series using all continues. I really sucked...