When you build a solar you should be picking a caste that fits how you want to play. Wanting things outside of that is fine and expected, but if you need four excellency purchases to make your build work from the start then you're doing it wrong....I mean, yeah, if you've resigned yourself to 'I'm A Dawn Caste, I don't need subterfuge or crafting or empathy' I guess that's okay?
Or if you're lucky enough to be a Night Caste who likes guns and has no interest in tech or crafting and is a pathological liar - their Excellency is pretty good. Otherwise I'd say yeah, one Infernal charm that does what you'd need conservatively three or four Solar charms for is by definition better.
Even then they still get all the benefits of the full excellency set they did buy.
If you want all the advantages of a dawn caste and also to hand craft your weapons you've got to pay extra for that.
There's an advantage to the way infernals do it, but it isn't three charms worth of advantage.