I think Colin should do his American Smooth. I'd like to see his Cha Cha again now that he's come on so well. I think Zoe should do her Samba because she needs a fun dance poor girl...and I actually liked the Brazilianified Age of Aquarius!
I recently watched Natasha and Brendan's DVD in series I and Brendan said he chosed Samba & Quickstep because it was a grand final and therefore they expect something more exciting and festival feel. For the same reasons I think the couples this year would probably choose something which is not necessarily their favorite.