The BB735 has the same pickups as the BBP35 and the body is laminated in the same way and with the same woods, although the P35 has higher quality selected woods and the 735 uses more generic sources.
The main diference really is in the details, in the same way that a premium Fender Jazz Bass is a lot more expensive compared to a standard or a mexican one. For example, the Fender Jazz Bass American Original 60's Jazz Bass costs 1800 euros and the Fender Vintera 60s Jazz Bass costs 850 euros. It has a bigger price diference than the one that we can see between the P35 and the 735a.
I have the BB735a and it's a great bass. Really well built and the fact that it's active/passive gives it more tonal options compared to the rest of the other models of the BB series. But the P35 has better craftmanship. First, most of the work is made by hand in Japan and the quality of the built is trully superior. I stands side to side to the higher line Fenders in the market, and I dare saying that it would be more fair to compare it to Custom Shop builds than to the higher level production line by Fender. You can feel it in the neck, in the way that the wood resonates, and also in the way that the whole instrument plays.
Then you have the IRA tratment that is a proprietary technology by Yamaha that can only be applied to a single instrument at a time. Therefore, it delays the production time and also promotes for a better acoustic response of the instrument.
You get a great workhorse with the Yamaha BB735. It's trully a musicians tool and can deliver everything you need on a bass. But the BB35 is a better instrument in the sense that as higher build quality and better components. Is it trully worth the $700 diference? Is the American Original trully worth the almost €1000 diference to the Vintera? I guess that a bass is worth what you're willing to pay for it. From what I've seen around here, people are super satisfied with their P35 so maybe it's worth that money for them.