John,
The main difference between butterfly heads (CCIR) and the 'normal' heads (NAB) that you find on most machines is the gap between the two tracks on the tape. NAB heads have 2mm spacing between the tracks where butterfly heads have 0.75mm spacing.
Butterfly heads only make sense if your tapes are recorded that way or you record them yourself with these heads. If you play a tape back that is recorded with NAB heads, like the TTP tapes, you will lose about 1.5dB of signal to noise ratio. There may also be the risk that your butterfly heads pick up unerased crap from the 2mm gap of an NAB tape, such as a time code signal. (Not with TTP tapes obviously, since they are recorded at on new tape stock) There is however no real penalty if you play back a CCIR tape on NAB heads.
So, in summary, don't spend a lot of money on butterfly heads unless you do some recording of your own.
A different question: Is the capstan of your C270 completely silent or can you hear some whine of the motor? My C270 is a bit noisy in that regard, even though it doesn't show in the W&F spectrum. I have not been able to find any reference whether that capstan noise is normal or not. For me it is just a little bit too loud, which makes it sometimes annoying.
