Pretty sure you meant stay away from Turion X2 and Athlon X2. These are K8-based... an architecture from 2003.
The new Turion II and Athlon II are actually not something to steer clear of. They are based on the K10.5 architecture, which comprises the Phenom II desktop processor series.
The Turion II compete with Core 2 Duos clock for clock. And obviously, they are cheaper, and come with better integrated graphics. And a 128b FPU, if anyone cares.
From what I've read, a Turion II Ultra M600 @ 2.4GHz (AMD's top of the line) is slightly below the Intel C2D T6600 @ 2.2GHz and that's a 2MB L2 cache, 800MHz FSB processor (like the popular T6600 series). This is according to a synthetic cpu PassMark test (cpubenchmark.com). I haven't seen any "real" benchmarks comparing the two, this is all I've got.
Intel's C2D has variants with 3,4,6 MB of cache and/or 1066MHz FSB, so the C2D should pull away handily with these higher end processors. Not to mention the chipset handles faster/lower voltage DDR3. Generally the AMD's will have higher power draw as well.
Honestly, unless you find a really great deal, I'd stay away from AMD mobile's right now if gaming is your primary use. I wouldn't recommend a C2D either, the Core i3's and i5's aren't that much more and are that much better. When the Danube platform is released, AMD will have a good quad with DDR3 on the market, improved battery life and discrete DX11. But even then, per core, the AMD's are still slower and more power hungry than the Core i3-i7 series.
I'm an AMD fan btw, it's just not a good year for AMD mobile cpu's (actually that's been true for quite awhile). While Danube will be more competitve, things aren't going to get interesting until 2011: 32nm Sabine/Llano.