I can't speak to 5-string but earlier this year I was deciding between the BB234 and BB434 and went for the 434, largely because I figured there was less of a liklihood to need to upgrade parts. The price difference new between the BB234 and BB434 was ~ AUD 229, but ultimately I decided it was worth it for me.
The 434/435 has a 5-piece neck (not on the 234/235) with a 6-bolt neck joint (compared to 4-bolt), an upgraded Graphtech nut, D'Addario strings (compared to generic Chinese strings on the 234/235), Alnico V pickups (compared to ceramic), upgraded bridge, and string-through ability (missing on the cheaper model).
My biggest disappointment was the inability to get the BB434 in white. I got the Tobacco burst which is... fine, but I would have preferred white and then I'd change the pickguard to white or mint.