TD humourously gets easier on higher difficulties because you gain spirit so much faster and can thus enter trance more often to obtain more resources.
You can not tell me with a straight face that lunatic is easier than hard in that game, or hard > normal, or normal > easy.
SA is pretty universally accepted to be one of the hardest games to learn and ubiquitously the most punishing, while UFO is generally considered the hardest on higher difficulties.
Personally I also have problems with the system of the post-PoFV games, but more due to its life and bomb pieces being split up, and the lack of point-granted lives that otherwise rewarded strong play with the chance to rest more easily. Having to go out of my way to get a mere fraction of a life makes it feel not even worth it, while missing a point item can be made up for by getting points by other means.
I find TD more punishing than SA-you can bomb through SA relatively easily. UFO isn't that punishing due to so many opportunities to gain resources-I'm not saying those resources are easy to get, but I'm saying they are there! (note: I'm only good enough to get them on lunatic with a plan TO get them, and messing up my route results in getting a lot less overall). On scoring lives...EoSD you get all of them , PCB you get the 800 or 1000 extend, maybe 1200 (or 1400 if scorerunning), IN you get all of them, PoFV good luck getting the 90,000,000 extend when you're going for a first clear, let alone the 70,000,000 on any difficulty but lunatic and even the 50,000,000 extend is a challenge at that level on normal. MoF you get them all easily if you're skilled enough to clear, SA you get 10 lives to work with, minimum, UFO you get at least 5 assuming a Nue capture, but you can get up to 16-17, and TD gives you 6-8. That you have to fight for.
So really, TD is the most punishing.
PCB or IN is probably easiest to clear, assuming you don't bomb everything in MoF.
SA or UFO are hardest to clear, depending on how much you bomb, go for UFOs. I found them equally difficult to clear on normal, though since I've done 8DNB normal SA (bad) and 2DNBNUFO, well, UFO. I think that says which one is trickier on normal, in my opinion.
tl;dr: TD's difficulty widely depends on the player and how likely they are to derp and stupidly lose resources, SA's depends on how much you pre-emptively bomb/die with bombs/dodge at low power, UFO on UFOs, MoF on how much you bomb.
The hardest Touhou games are the newer ones from TH10 on. The fact that ZUN only gives you 2 lives to start off with gives me RAGE. ![Sad :(](/forum/Smileys/default/sad.gif)
Well, you start with 2 lives in all the games...
![Wink ;)](/forum/Smileys/default/wink.gif)
Just use the resources you have carefully and practice and eventually you'll pull through.