3 is longer so proboably concidered harder overall, tho personally i always found 4 more of a challenge (not that i sat down and completed either one tho
3 seems to go crazy on the player right away, 4 gets hard in a more balanced fashion. 4 might be hard simply thanks to the type selection. While the G4A (vertical mine type) seems to be the popular choice it's with good reason. Vertical mine cleans up the tough sections but I think for beginners isn't too easy to control. However, the Armor Piercing laser of that type is not very good, somehow though everyone seems to use it for Stage 3 (bubble) while I don't find it very useful at all.
Nice clip all the same, better than alamone's at times. Watching it makes me want to practice again.