Hey leafy, for the record, I'm referring to the coils that look like this:
these are the ecotec ones, they look more like COPS, and have been around since early/mid 2000's. I see them on 06 2.4 engines like the cobalt. The terrain ones are more near 08 inception. Looks like 08 equinox. ** correction, actually these first came out on the 04 CTS 3.6. List of vehicles with these coils here : http://en.wikipedia.org/wiki/GM_High_Feature_engine#LY7
However, the version from 2008 onward CTS/STS is Direct Injected, labeled the LTT. Typical DI coils put out around 86mj (compared to LS coils 90-120mj, or toyota cops <50mj) at 120ma secondary current. They need to be stronger in DI applications
Ecotec 4cyl coil above. I would call this kinda a weird COP more than a pencil coil, where the electronics are partially/mostly in the sparkplug well.
This doesn't mean much, but it just shows the evolution of the design, much like LS2 coils, while similar to LS1 coils, are far improved, so would you be able to draw a similar conclusion about these guys.
I wish I had any sort of hard data on them, but all I can say is if I had to put money on it, they should be quite a bit better than the Toyota cops, and I'm hoping in the range of LS1/LS2 coil power. They use the same connector as the lastest version of GM LS coils, as well. I'm going to try and do more digging if I can.
*** More reading.
Anyway, Part numbers for the Non-direct injection pencil coils appear to be Delphi D501C, and for Direct Injection versions they seem to be D515c, the latter seems to be from 2008 or so onwards. Another version, D598A looks like its used in Cadillac's Newer V8s as well. I'm going to get ahold of a few of these and see what I can find out.