That's a very good point, Chris, which again is why I prefer SUTs 'set' for use with a specific MC cartridge, where results obtained are goverened almost entirely by the inherent characteristics of the transformers themselves. It's a 'source-first', hard-wired approach that, in my experience, works very well.
That way, you remove various breaks in the signal path, introduced by the use of dip-switches, for adjustment of variable gain and loading - the effect of which is significant, in terms of loss of integrity, when one is dealing with such minute voltages from low-output MC cartridges.
I'll always go with the 'purist' approach! However, that said, it doesn't seem to hold back Martin's H7 or his Whest, both of which feature the use of dip-switches. I guess that they're just very well executed!
Marco.