What is best is the product that is still effective (no resistance issues) and meets your needs with the least amount of dosing possible. This is because the more often you dose with a dewormer the faster resistance to the drug used will develope and resistance is a major major issue.
Every horse owner should assess the risk factors of their horse's situation, find out if there horse tends to have a high natural resistance to parasites or needs more frequent testing/deworming and then build a deworming program to fit the exact needs of their situation.