What quality would you say iphones have?

Are they better quality then the Samsung s4

Very good quality and way better quality than the Samsung s4.

This is more of a Apple vs Google question, which comes down to preference. In a nutshell iPhone is a more stable device due to the closed source and tightly controlled user experience, but you lose various freedoms. Android is way more powerful and versatile due to its open source and uncontrolled environment, but you have to deal with things like more frequent crashes and undesired side effects. I prefer Android but I'm a power user and have a strong background in everything tech related. I like more options and freedom. I enjoy dismantling things and seeing what I can do. It comes down to what you want.

if your asking about build quality of the physical device, Apple will usually win that. There's only 1 company making iPhone and quality is tightly controlled. There are so many Android devices that vary vastly in quality, and the Android operating system is not as stable as Apple's.

IPhones are made with metal and glass, Samsung Galaxy S4's are made with plastic.

I say the materials a phone is made with don't make a difference to a phone's performance. It's the features that matter, not the materials a phone is made out of.