Ignoring money, both GM and C2 can be equal performers, with everything depending on the ability of the developer. But for the money that it's worth... yeah C2 is a better bargain.
Indeed! There seems to be a lot of hate for GM on this forum, but the truth is that they are both great tools and have their own inherent strengths/weaknesses.
I started out with C2 at the end of last year and I ended up getting so frustrated with poor performance on my platformer that I ended up buying a pro GM license a few months ago. Currently I am developing several games in both applications, so am quite aware of the pros/cons of each.
GM kills C2 in the performance stakes, since it does native exports. It also benefits from having features such as paths, timelines, scripting, per pixel collisions, debugger, SVN , etc. Wheras Construct is much faster to use and has a more elegant workflow/gui with a nice layering and events system. While using the event sheets is great, at a certain level of complexity I would much rather be scripting it!
And if C2 had native exe export I probably would have never even tried GM! This is why you are paying so much more for the full studio version of GM, as the standard and pro versions are actually cheaper than C2. YoYo have many more devs than Scirra and most likely most of them work exclusively on the exporters. I would be more than happy to pay an extra few hundred for an exe or apk native exporter for C2!
For my projects that will be aimed at the desktop/mobile/Ouya market I will mostly use GM and for the web I will use C2. For non-web destinations, C2 is too reliant upon 3rd parties which is too much of a unknown for me at the moment. HTML5 for games will certainly be viable for games in the coming years, but if you want decent performance on older machines and mobile, it just isn't there yet IMO.
As always, you need to pick the tried and true tool for the job. Like the saying goes...If the only tool you have is a hammer, then every job looks like a nail...