Your views please!

I've offered to make Nikki a cushion, and thought I'd try something different.  I found a gorgeous Starburst quilt on Film in the fridge, so I followed the excellent tutorial that accompanied it, thinking I'd make one block for the cover of my cushion.

Apologies for the poor pics (midnight in our kitchen on an iphone!)

Here is the block in progress...

and where I'm up to now. 

The thing is, I can't decide whether to:

a) follow the tutorial and trim this to a square.  I'd then need a border for a square cushion or I could put the square onto one end of a rectangular cushion (I'm thinking I'll use my grey flecked cotton for the borders)

b) or trim this block to a circle and applique it onto a square cushion?

Hmmm it's a dilemma I can't face tonight so I'm going to bed, but your views would be very much appreciated!  (including yours, Nikki!)

x