Jabiru vs bolly propeller
The design differences can be seen from the images etc... the Bolly props are Carbon instead of glass, have a smaller blade stem, different hub, different bade profile, blade area distribution etc. I think I'd be right in saying that a 2-blade Bolly prop is lighter than the Jabiru prop. They're both great products, with similar performance, abrasion/rock resistance etc.
I'll put a couple of points in here, but I work for Jabiru so no prizes for guessing what my answer will be! But I'll also say that I've never flown behind a Bolly prop so I can't say first-hand how they compare.
Jabiru engines, particularly on faster airframes, do better when a prop with smaller blade area is used - it allows the prop to "slip" on take-off, increasing engine RPM and improving performance - so I'd definitely opt for a 2-blade type. The old "3 for show, 2 for go" rule still applies. We've also tested the crankshaft stress and resonance with the Jabiru composite props and we're happy that they're not causing any mischief to the engine - the main reason we opted for fibreglass in our design. The larger stem on our blades also reduces the stress in the hub area and helped place the blade resonant frequencies where we wanted them. Finally, last time I looked the cost and warranty side of things come down in favour of the Jabiru prop.