I've experienced Construct 2 as blazing fast.
rilem.nl/sheep2
This runs at 60fps on my 2 year old desktop.
I'm working on projects at the moment which are more graphically intense and still run like a charm (in web-browsers).
Check out this video I did on C2:
If you're really serious about using the scirra tools to make a full fledged game I strongly suggest using C2. You might only think about desktop publishing now. But what if you change your mind in mid development?
Is the extra bit of performance you might gain by using Construct Classic worth it, if you can only deploy to one platform versus basically every platform with C2?
Anyway that's my 2 cents.