For me the most comfortable bars (rando or "regular" drop) have tops and drops that are very close to parallel. Take a look at the side views on the first page. On the 135 and 177, the tops slope down quite a bit compared to the drops. On the 132 they're both pretty much horizontal. THAT's the big difference in my book. And that's why I use 132's.

SP
OC, OR
ps - if you're looking for a wider rando bar, VO sells one that goes out to 48cm, IIRC.