The big volcano is one of my favorite "alternate routes". I recall being stuck in Easter Island 4 for the longest time, so this level was a huge surprise when I first played it, and it was a good one.
Morgen makes (or made) this race very interesting. To me, this level is funner than Easter Island 6, mostly because of its level design. I prefer the original direction, sunny weather, and AI programming, and I'm more familiar pushing cars Out in this direction.
Level 6 removes the barriers in the volcano, but it's not a huge plus for me, as I tend to struggle pushing cars into the lava. Other than that, I find Easter Island 5 to be more exciting - faster-paced, yet less tricky.