Second officers have one stripe, after about 4 years promoted to Junior FO with two stripes, six - eight months after that promoted to FO with three stripes. At least you are focusing on the important things if planning to apply to CX.
What's the difference between a pilot who had to pay his way through training compared to someone who was sponsored by an airline.
You are right there is no difference in what you say. Some cadets are good, some not so good as initially real world experience is severely lacking. If however someone who joined as a cadet makes it all the way to the dizzy heights of captain with CX you can be sure they are there because they are able and competent, having gained a lot of experience working for the airline.
What you are actually referring to is not the method of training or who paid for it but what happened after the training. A cadet will join CX as an SO with a couple of hundred hours. Having flown around Adelaide in good weather doing pretty benign things, circuits, couple of good weather x-countries, some night landings in good weather etc etc. A non cadet SO would have done the same things during training but after that spent the next 5-10 years flying in the real world, light twins, twin turboprops, regional jets/turboprops in all maner of weather and in all maner of circumstances. Frieght/airline ops/military/aid work etc etc etc. After gaining at least 3000hrs doing this flying they join CX as an SO.
It is not about who paid for the training but what happened next, that is why some cadets are incompetent. Some, not all.