Similar dilemma. When I bought my 147 at Christmas, I seriously considered the 156 Sportwagon, same spec level, but as a 2.4 JTD. But it was going to cost about £5k extra and at the time, that was £5k too much. If I was going into the dealer tomorrow, I would without a doubt order the 'new' 156 Sportwagon in dark blue metallic, tan leather, 150 bhp JTD, roof rails (gotta have the roof rails!)and especially with the new '147' style interior. (The old interior put me off compared to the 147. Liked the style, but the choice of materials/finishes etc, just don't compare).
Like Stef says, best looking estate on the market. Sorry, Sportswagon!