Okay, well...
The H bongo has a three-band, 18 volt preamp, a neodymium pickup and a basswood body.
The Big Al H has a four-band, 18-volt preamp, a ceramic pickup, active/passive switching and series/parallel switching, and now (on the 5 string at least) a mahogany body.
There are many more differences than similarities. They're bound to have a totally different vibe.
More options are not necessarily better. I have a Bongo HH with piezo and also a Bongo H. I gig with the H because it's lighter, and fits the vibe of my current band better. It sounds fantastic. So does the HH with piezo, but it sounds good in a different way.
Why would you buy a Bongo when you have the Big Al available? Simple. Because you like the way it feels, looks, plays and sounds better, should that be the case. In other words, the exact same reason why you'd buy any given bass over any other bass.
The whole idea of the Big Al replacing the Bongo seems silly to me. I mean, look at the Fender catalog. They sell 33 variations of the Jazz bass, fercryinoutloud.