Start with the reader, not the rate
Most program directories sort by commission rate or EPC. That is the wrong first filter. The first question is whether your readers would want this product if you were not paid to mention it. If the honest answer is no, a 40% rate is irrelevant: readers will not convert, and the ones who do will return the product and remember who sent them.
The second question is whether you have used it, or can. First-hand use is what separates a review from a rewritten product page. Google's Search Quality Rater Guidelines added "Experience" to E-E-A-T in December 2022 for exactly this reason. If a merchant will not let you test the product and you cannot afford to buy it, think hard before recommending it.
Only then look at money. Here the details matter more than the headline. A 10% rate with a 24-hour cookie and aggressive reversal rules may earn less than a 6% rate with a 30-day window and a merchant that pays on time. Read the operating agreement in full; it is usually a few pages, and it is binding on you.
Finally, look at the merchant's behaviour outside the program. Check reviews on Trustpilot, complaints with consumer bodies such as the Better Business Bureau in the US or Citizens Advice in the UK, and long threads on affiliate forums. A merchant that treats customers badly will eventually treat affiliates the same way.
