kochiwilliam From my experience it depends on what type of game / app you want to use construct to make, as well as your preferred platform to deploy. It also depends on how much free time you have improving your programming skills. (If I had more spare time and less hobbies I know I'd be better off learning either unity / unreal to make games).
I used to use klik & play, games factory, mmf and fusion products. When I found C2 I loved the improvements it has on the event sheet side of things. It was way more intuitive and almost a seamless transition form the click team products. Trying to go back to the Click product now is a chore as i am so uses to how C2 displays its visual events and feel its so much friendlier. (Click team are updating the events in their upcoming software to a more similar style to construct)
I've had a full version of C2 for several years now and tried C3 free edition. I would update to C3 now that there is a desktop version if the plugin's from c2 were all supported. Plugins gave great freedom in C2 and allowed me to create many game ideas / projects quickly. They are now the reason I am stuck with a half broken C2 product with no real support as I cannot move my projects into C3.
With regards to your question on how powerful C3 can be. I've found this to be hit / miss depending on what you want to do.
Do you plan on creating PC or mobile games? And do you have a genre in particular?