There is no perfect pellet. They have all had some quality control issue somewhere. Popular ones are manna pro series, purina, nutrena, kent, and penpals. Your local mill has some impact on the quality. A lot of people find tons of corn in their manna pro when we have never found a single piece. Mills like to flush the system with corn if the design can't handle what they are running through it. Several people have had issues with kent but we never had. We've used nutrena occasionally also without issues. Maybe it's just our local ingredient sources and mills. Some have gone to local only pellets that don't have an impressive ingredients list but had more luck with quality control. Many of these cheap local pellets don't have a useful ingredients list. They use vague names and all inclusive terms to allow them to basically throw in whatever they can get cheaply and in good condition at that time of the year so long as it keeps the nutrition breakdown the same.
Everything has positive and negative points and some controversy around it. Mainly you need to find something consistent in your area that your rabbits can survive on and then just keep breeding the ones that do well. Eventually they will be bred to thrive on your pellet.
