Understood Rabs.
I'm not sure if I could narrow it down to any one song. Harris's stuff tends to flow from song to song over an entire album. I'm not sure that he'd really get your point from just one song.
I guess it's just a question of where he's coming from as a player. If he has experience with very straight ahead rhythm driven music like Maiden, then I guess he'd find Harris easy enough to play. If he doesn't have that sort of experience, then he's gonna find that it's harder than it seems.
I'm not sure that being experienced with Jaco-type tunes would really prepare a player to handle Maiden-type metal tunes. Stylistically, they're worlds apart.
Technically speaking, Jaco's stuff is superior, but like any style of music, it's all in how much a player can adapt to feel the groove of what's going on. I guess it's more a question of 'feel' than it is of technique.
This reminds me of a band I threw together in high school years ago. We were doing shows at the schools several times a year, and as one show was approaching, I was having a hard time rounding up my usual bandmates, especially a drummer. To make a long story short, we recruited a Jazz drummer we knew, who wanted to give the Metal/Rock stuff we were doing a try. He did a great job learning the songs, and he technically had no trouble performing them. However, no matter how much "coaching" we did with him, he just couldn't sound like a Rock drummer. He'd play the parts perfectly, with good timing, etc, but he just couldn't get the "feel" down. He'd play the parts too stiffly. He'd not accent his cymbal crashes, etc correctly. No matter what we did with him, he couldn't help but sound like just what he was: a Jazz drummer playing Rock music.
Now, I'm not saying that that has anything to do with your friend, this discussion just reminded me of that.
Anyway, please let your friend kow that we'd be happy to have him, and I for one would'nt mind stretching out and doing some other stuff if that's what he'd be into. Although, if he's on the bass, I won't be of much use to him.