Well, for me it was the right length, the right look. It wasn't a quantitative thing. At the right distance, it made the right picture... for me. Like everything else, it's more a question of 'feel' than technical performance.
The 135 was designed without a focus mount, to be used on a bellows. But with the focusing mount, it was a neat lens. Under normal circumstances, expensive though.
For all around use, the 150 is probably better for most folks most of the time. No bad choice here, though.