i use Purolator for oil filters and I drive out of my way to get them. Around here Fram and Purolator are the 2 brands that are sold through the discount houses with most places selling Fram. But if you look here:
you will notice that the Fram oil filters pictured all use cardboard end caps. The Purolator and most others (like Motorcraft) use steel end caps.
For the rest of the filters like the air filter I just buy whatever is cheapest. But these filters are completely exposed not sealed in a can like an oil filter. So it is easy to see when the manufacturer is cheating with inferior components. The Fram air filters and the Fram oil filters for motorcycles that are exposed are identical to the competition in construction. So I buy those.
For your Zetec just get the Motorcraft plugs. And make sure after installing your plugs to check the torque on them a few days later to make sure one of them hasn't loosened up.