I beleive the snarget hole is an even cave to start with.Meaning that there is no hesitation,although the ending boss is an eyepopper at 1st the you think holy *****! Then once the purple spray is used you then could think that it is now easy and not difficult however freezing it at a wrong angle such as...well freezing doesnt work i now remember.My suggestion,use white pikmin to attack it unless your up for a challenge of course just easily use yellow pikmin easily able to reach the snargets head...but then again the most difficult type to fight the peleading snarget is of course, the purple pikmin.
Anyway the treasure gathering difficultyis not sever to rate it would be a 4
enemies a 6
obstacles a 7
in total the cave evens out to a 5
P.S.I rated everything from 1 to 10