Construct 2 for sure. It's easier to use, updated frequently, powerful and has a great UI, cheaper, etc.. Before you buy it give the free version a go and follow granpa 's advice to recreate the same thing in C2 you made in Stencyl.
Your biggest problem will be running it on MAC. You'll have to use a VM software to do that. Construct 3 will support MAC, but it's still a long way off, so don't wait for that.