The answer is it depends. The zirconia (all porcelain) option is the strongest. The acrylic option is not as strong but often looks better cosmetically. Having an upper and lower zirconia all on four will often produce teeth clicking sounds that patients find annoying.
Then there are biting and wear issues. Zirconia is a better choice when the opposing teeth are natural or crowns especially if grinding is an issue. if an upper and lower all on four are done it the same time I will often make the top zirconia and the lower acrylic. Excessive grinding with upper and lower zirconia can place heavy strain on the dental implants and cause failure.
People lose teeth for different reasons including cavities,gum disease ,grinding and sometimes a combination of more than one. The plan to replace your teeth should consider those factors. Your dentist should be able to guide you to the pros and cons of both materials and make a decision that would be the best for your situation