ECA's have been graded. I would recommend checking whether they have been graded as 5 star, 4 star, etc. It is a starting point.
Next, locate the ECA Local Pay if they are close. Meet them. Buy something from them. If you are happy with their product & service, you have answered your own question.
Talk to other affiliates to see what they thought of Local Pay in their area. A2A friends could be very useful for this.