Don't know what 10 bolt you were running. However the 9" has many advantages over a 10 or 12 bolt. First off you don't need to install c-clip eliminators. It's much easier to setup gears when it's on the bench and not under the car. You can setup several gear combinations and swap out for different tracks, in your case 1/8 or 1/4. The nine inch ring gear is stronger than the 8.25" or 8.5". The housing with backbrace is stronger than a cast center with steel tubes, really no good way to brace a 10 or 12 bolt housing. Far as the bearing caps go, I don't think they're smaller but wouldn't swear to it, never had an issue with them.
Just my $.02
Bill