rank them purple coin missions!
Maybe I'm crazy, but the path for Luigi's Purple Coin Chaos is almost identical to the one from Luigi's Purple Coins. At least, the way I do it. The trickiest part is probably a tie between accurately collecting the first 30 coins, and the final 10 coins when sometimes I might screw up and leave a purple coin hanging over a disappearing green platform. Not a fun moment, haha.
I think you may be right that the purple coin missions in the first SMG probably being a tad better overall. I mean, there's still a good chance I might mess up and die in most of those stages, whereas I'm well on my way to memorizing the ones in SMG2. The only exception is Purple Coin's Beach Dash since me and the dash pepper aren't the best of pals!
Oh and I probably should have ranked Bulb Berry's Purple Coin Glow lower since now I find it way too easy and short.