Static Class vs Static Struct for static tool operations?

I need to create a "tools" class or struct with only static methods. As someone coming from a PHP background, structs don't really exist.

I was reading about this Why Choose Struct Over Class? but they do not talk about static structs or static classes.

Which should I use for static methods that are never instanced and why?

Example:

struct BasicTools {
    static func split(str: String) -> [String]{
        return str.characters.split{$0 == ","}.map(String.init)
    }
}

vs

class BasicTools {
    static func split(str: String) -> [String]{
        return str.characters.split{$0 == ","}.map(String.init)
    }
}

In use:

let StrArr: [String] = BasicTools.split("example,example2,example3")