The 2J is a better engine in pretty much every sense, better design, materials, reliability etc. The thing they share is capacity and number of cylinders but not that much else!
The bore and stroke just describe the characteristics of the engine e.g. revvy/torquey . The 7M is a lovely torque monster but the 2J is rightly famous as one of the best engines you can buy. 130bhp is standard family car territory, 200bhp is pretty quick, 300bhp is fast and 400bhp is about as fast as I think you can use on the road properly
There is no hesitation at all in recommending the 2J, more power and much stronger and better reliability