I'll try my best.... Both are great basses. The BB424/424X is a fantastic bass that will out-P-bass any Mexican Fender. It also has the option of adding in J-bass tones from the rear pickup. 100% passive. Great, aggressive PJ.
The TRBX504 is equally good, just different. The active tones on it are brilliant. The passive tones are just as nice. It will get very close to a P-bass tone in passive mode but it's not exactly the same. Less aggressive than the BB424.
The TRBX can get close to what the BB does but not the other way around. If you always use passive tones, get the BB. If you need more versatility get the TRBX.
Both basses outperform instruments costing twice their price. They're both fantastic so you really can't go wrong. Though the right answer really is........buy both!