I own both the Yamaha TRBX304 and 504 basses.
I have no experience regarding Yamaha 5 string basses.
I purchased a Yamaha TRBX504 shortly after the TRBX304 and do not regret it.
The differences are that the 504 has alnico pick ups, active electronics, an active/passive selection switch, and I believe a different active electronics circuit.
Keep in mind that my basses are both 4 string basses but I would think that the Yamaha 305 and 505 5 string basses follow the same parameters.
So, to answer the OP’s original question, IMHO, these differences more than make up for the cost difference between the 305 and 505 so I would pick the TRBX505.
Here is a link you may be interested in on the differences.:
I hope this helps