RS4 vs. RS6 comp wheel
 

I found the RS4 and RS6 compressor maps (below), and was surprised that the RS6 map does NOT show large flow capabilities? I expected a larger difference based on the dimensions (note: RS6 exducer 5mm larger than RS4)
RS4 shows max of 0.18 m3/sec
RS6 shows max of 0.19 m3/sec

Comp inducer: RS4: 40.5, RS6: 42.5
Comp wheel: RS4: 40/51, RS6: 42/56
Blades: RS4: 8, RS6: 8

What gives?

RS6:
Attachment 29768

RS4:
Attachment 29769