For me it's simple. A decent active FRFR with all the DSP to make it a blank canvas enables me to spend time finding a pre I like to give me the tone I like without having to juggle an extra myriad of variables in tweeters, crossovers, speakers, amps etc that you get from a traditional bass setup. For example, with a traditional bass cab, the baked in sound of that speaker cab can really mess with you if you don't clock that it's that part of your setup which is dominating your tone.
With the modellers that are out there, you can twiddle to your hearts content... but conversely, you can just find that one pre that you like and just concentrate on getting on with the music.... and as Frank says, the fact that you can have your core tone and then push in extra instruments and use it as a monitor also... brilliant. Vocals tend to send a bit crap through bass rigs.