I bought a couple different styles recently. The eastwood stuff seems to be too deep black in color.
As far as the 3M stuff. I have been using it since the late 80's. I know for a fact that it wasn't always the sticky messy type that it is now. Maybe it was changed to that style in 2004 as indicated in the reply from 3M. Regardless, I don't believe the current 3M style is correct at all in replicating what was on the cars originally. It works and makes maybe 95% of folks happy, but if we're going for authenticity, it simply does not hit the mark.
As far as defining the term 'rope caulk', I don't know if it's just a generic term, but most definitions I have found say it is putty based. https://en.wikipedia.org/wiki/Rope_caulk
The 3M stuff is most definitely butyl-based now, more like butyl cord or butyl tape.
Ford assembly manuals note ESB-M4G32-A, black sealer, .19" diameter
Synthetic resin plastic sealer
This sealer is specified for hand application and is applied in daubs or extruded beads or ribbons as required
SAE standards page for 'Synthetic resin plastic sealer':http://standards.sae.org/j250_195905/