Hi Penny,
Congratulations on your new puppy. My 5 month old Golden Retriever (also called Dylan!) has always been fed on Royal Canin. Some puppies do go off their food when they are taken to their new home - the stress of a new envirnoment, being away from his mum and brothers and sisters, etc. I would persist with the Royal Canin for a while. How many days has he been with you?
My Dylan likes his food moistened rather than completely dry (just a couple of teaspoons). You could try adding a couple of spoons of evaporated milk or rice pudding to it and mixing it well, then he couldn't just pick out the 'nice' food. Dylan had this for the first few weeks, until he went off the evaporated milk. On his other meals, I sometimes put a spoon of tinned pedigree puppy food and mixed it well.
I believe the problem that people have with Eukanuba is that Iams is perhaps responsible for animal cruelty. Take a look
here for more info.
HTH, someone with more experience will be along soon I'm sure.
Sarah