I consider both "GT" cars. The areas where the BMW has more weight due to luxury (though an M6 have much more than the Camaro would) are made up for by areas where BMW cut weight through spending like the carbon fiber roof. That's why I considered the two comparable.
For what you are talking about in a 2+2 coupe the Lotus Evora fits. You get the lightness (by around 1000lbs) and the fuel economy, but it costs a hell of a lot more, the interior makes the Camaro look like a Maybach, and you get the engine from a Camry.
The LS9 is over 500 lbs dry from what I have read. The supercharger, intercooler, and additional plumbing leave their mark in that respect.
I personally think the Camaro looks good. That is a matter of personal taste though.
Supposedly the interior is better too, but I've never sat in one so I don't know how accurate that is.
Either way, if someone wants a very high performance 2+2 they can get this Camaro, the GT500 (with similar interior issues), or they are spending a ton more money. Really the only car that fixes all the complaints people have expressed about this Camaro is a 911 Turbo. The complaints I've heard are compromises GM had to make. The 911 shows that while those compromises can be avoided it costs a ton to do so.