Can I just say that the major difference between accuracy modifiers and evasion modifiers is that the opponent has control over the former? Unlike evasion modifiers, which affect the Pokemon using it, the Pokemon who is getting his accuracy reduced can simply switch out and reset the accuracy loss. The opponent's evasion gain, by contrast, is permanent until the opponent switches out, making it much more difficult to play around and, consequently, much more luck based, because you're literally sitting their twiddling your thumbs praying that you hit the opponent with something, anything, and with any Pokemon rather than being able to weigh your options and say "okay, so, I have lost --% accuracy on all of my moves against this Pokemon, basically, and I can either switch out to something that can also deal with it and then bring back the other thing in later should I fail, or stay in and toss the coin as to whether or not I hit it".
That is a huge difference.