I play piano, percussion, and i used to play the 'cello, and i agree that percussion exams seem easier.
I think a reason for this might be that we have played the piano and we know the layout of the xylophone keys - it's a lot different to a stringed, woodwind, or brass instrument where you can't actually see the black and white notes layed out in a row in front of you, if you know what i mean.
I took my grade 8 Percussion last month and got 138 - if i hadn't lost 5 marks on my bloody scales i could have been into the 140s
but anyway, yeah, percussion does seem easier, but you do need natural rhythm, a good sight-reading ability, and you have to admit, getting a triangle to produce the right kinda sound with the right amount of resonance is no stroll in the park!
and alvin, snare drum IS boring, but i love tuned percussion and timpani, so it's all good