The General consensus for swing path is a slight inside to outside to outside swing path to meet the ball at the centre, and follow through around the body. 

 

A good way to think about this swing path was thought out by Golf align (“Golf Swing Plane Tips: Learn Proper Swing Plane”) as a one plane swing, where your clubhead is aligned with your shoulders throughout each aspect of your swing. So it starts a little inside, so you can rotate through the ball, and will allow you to hit more consistently as your swing will be similar each time.

 

The swing path of straight, but slightly inside to outside, will help you rotate, as if it comes straight up, it is difficult to drive forward without rotating your body, which would result in a misaligned swing path.