I like to think of Iams, Eukanuba, Purina, SD and such like feeding fast food to your pet. Yea - it's fine every now an then, and it's not the worst thing out there - but there are just so many other better options out there. Your vet will probaby reccomend Science Diet - because that's what they were trained with in vet school. Vets are not experts in animal nurtition - you need a nutritionist for that. Just like you wouldn't go to a dentist to have your eyes examined.
The dogfood project website is very helpful - lots of good tips, why things are good and bad.
I think the canned vs. dry food is something you'll have to decide on your own. I feed dry - because it's more in my budjet, canned food can be quiet more expensive.
I personally feed Blue Buffalo - I think we are using the Wilderness bag right now, but I've also used Orijen puppy. Both are what I concider to be great foods - for different things. not every food works for every dog. I have a cat that will break out in an allergic reaction and rip her face apart - unless she eats Purina. She's an old lady - so I'm not pushing anything new on her. When she is no longer with us, I'll look into switching my cats to a better food.
The higher quality you feed - the better your dog will look and feel. Casey doesn't smell, his coat is super soft and shinny, his poops do not smell nearly as bad, his eyes and ears are clear and his allergies are not nearly as bad. He came to me eating Science Diet - but I switched him immediatly. I never regreted it, ever.