This is just a general comment / thought.  Just using Fractal and Line 6 as an example.
Fractal models the Amps they own or borrowed - or via the schematics they obtain.
Line 6 [ I'm %99.99 sure ]  
only model the actual Amps they own or borrowed - none are done via schematics.
So how can anyone  [ say me ]  .... even try to say Fractals or Line 6's modelling .... 
relative to the Amps they physically own or borrowed.... is more or less accurate than the other companys' processes ?
Maybe Fractal's Amps need to be updated because they weren't done right at the start ?
Maybe Line 6 doesn't update their Amp algorithms because they feel close enough is good enough ?
I don't know .... either way.
Hence why
 i.m.h.o one cannot be "better" than the other .... there can only be the one which a persons ears and fingers prefer.
Not sure why I typed this ..... but that's never stopped me before 
Ben