Rich rewards more than abundant.
Consider the two missions, both of which reward Grade 1 Biological Samples:
Tirsan Spice - Abundant Yield
Boma Breeding - Rich Yield
The abundant yield mission costs 120 credits, and the rich yield mission costs 295.
Additionally, the abundant mission requires 15 skill, while the rich yield requires 55 skill.
From this, we can logically conclude that if Rich didn't reward more (on average) than Abundant, there would be no reason to ever perform it, as it would be more spent for less gain.
(Alternatively, I have my own anecdotal evidence than Rich > Abundant, but I figured the numbers are better evidence)
As to your second question, the results of the mission are irrelevant - what matters is your skill in the trade skill compared to the minimum required skill level. The greater the magnitude of the difference, the lower the chance for failure. This is represented by color, with "Orange" meaning "most likely to fail" (but also guaranteed to skill up!) down the color spectrum to "Yellow", "Green", and finally "Gray", which is (I believe) a guaranteed success (but gives no chance to skill up).