Why should people buy authentic aftermaket parts versus the off brands on the internet? Coming from personal experience and buying both off-brand and authentic parts the results favor the latter. Occasionally you can get an off-brand aftermarket part that will hold up to the task but oftentimes they fail prematurely.
Buying off-brands can be tempting due to the fact that the price is significiant lower than the authentic brand. We can all relate to this scenario, your budget is 700 and you need new shocks and struts. The authentic option has coilovers for 750 dollars while the off-brand has coilovers for 350 dollars. It would seem feasible to buy the off-brand for 350 and still have 350 extra for other things.
The recommendation is to buy the authentic brand because your getting quality and reliabilty. Majority of companies stand by their product and offer resonable warranties. Another reason to buy authentic parts is due to the longevity and the cost savings over the long run.