One of the benefits is accuracy. Real amps have crossover distortion. And just like real amps, you can change the amount of crossover distortion by changing the bias.BTW, What are the benefits to modeling crossover distortion?
Another benefit is ability to cut through the mix. Tones with more crossover distortion require less volume to be heard clearly above the band. And in a dense mix, you don't notice the crossover distortion as much, but you do notice the ability to ride above the mix.