You could definitely go with either size. I'd demo if you can and maybe drop that weight. LOL. I usually ride a 140 Pure, but rode the 138 and loved it. 138 is actually the same size as my 140 Pure when stood up side by side, just measured a bit differently due to the shape of the tip/tail. I'd probably go 138.
I ride the '06 142---I am 5'10"/165lbs, however I demo'd the 2007 Transcend in both the 138 and 142 and I felt better on the 138. Finless was the way to go for me!! I'll be riding the platinum 138 when they come out!! I highly recommend this new shape---tons of fun to ride!!!
I am riding a 138 cause my absolute was a 141 and I did not want to go bigger. I was a little worried that I would have some issues but so far it has been great. I think it is actually a better ride for me. I am 6' and just under 190 ( and lossing some weight)