Melesse - Go with the S90. It is so much more capable than mass market point & shoots. It has a lot of the features of an SLR, but the portability of a small P&S.
The G11 has maybe a slightly better lens: longer zoom, slightly faster over the range. But then you're back into something bulky again, and you'll find that you won't carry it if you're not sure.
For this type of camera, you have to accept that you'll either carry it a lot and use it infrequently, or not carry it and eventually regret it.
I carry the S90 in a small Lowepro case. Most of the time, it is in my courier bag that I take to work. On day trips, I put on the shoulder strap and carry it that way.
One thing I've found that makes either of these cameras more versatile than my previous P&S cameras is the optical image stabilizer. I
rarely use flash any more indoors. With a steady hand, 1/6 s is hand-holdable on this camera. No more having to choose from super-noisy by sharp and blown out and no depth with direct flash.
I assume that since you're here, you know a good bit more about photography than the average person. Spend that money on the S90 and I bet you find the SLR stays at home most of the time. I love my SLR and its superior image quality, but after a while, I had to admit that I'm just not committed enough to carry it around all the time.
Here are a couple more shots from my S90. None of the indoor ones used flash. The white balance was fine, I just prefer B&W a lot of the time.