There's also comparison tables with some desktop GPUs in
Notebook / Laptop Reviews and News - NotebookCheck.net
The issue with mobile GPU comparisons is that you can't normally pair them with a crazy powerful CPU to eliminate the possibility of a CPU bottleneck. See for example HWC's review of the
Envy 6 where gaming is very likely held back due to low power x86 rather than the GPU side of the Trinity chip. Additionally, manufacturers will release different configurations of the same GPU - GDDR5 vs GDDR3 is the most common difference, in which the latter generally hits you with a huge bottleneck. If I were you, I'd look for a similarly configured (or weaker config) laptop on gaming reviews.