My fave in the SP line is the T3, although all the others IMHO will provide fine
professional sound quality-as long as the recordist knows what they're doing.
(a tall order with any mic

)
For example, on some singers (like me!), the C1 accentuates sibilance
like many other microphones that already have an "airy" top.
"Other microphones" include the Beyer M88, AKG 414 B/UlS, et al, so there are other well respected microphones besides the C1 BTW.
If you really know how to de-ess a vocal the C1 will still work fine.
In fact some pro AE's like Alan Parsons prefer emphathizing the top end first.
Interestingly, the C3 is somewhat flatter in response and is NOT the same in cardiod as a C1.
As each singer's voice isn't linear in response, you can find it difficult or impossible to differentiate between various microphones on commercial releases. For example if someone didn't tell you that all the lead vocals on "Pet Sounds" were tracked with a Shure 545(!), would you REALLY have noticed the difference vs. the U47's or RCA 77's used for the group vocals?
Chris