The former's inherent namespacing is exactly why I prefer it. You know exactly where each method came from (it's a method that exists in a `some_array` instance namespace); inversely, I have no idea where `has_my_thing(foo)` comes from or what all it can be used for if it's just sitting in the global namespace.

Very often, when I'm learning new code, there's one line I'll write over an over in console bindings:

    > some_object.methods

It provides a super-easy way to learn what methods are actually relevant to `some_object` without having to pour over every method available in the global namespace and figure out whether `some_object` is a valid argument to each. You can also apply set logic like `some_object.methods - {}.methods` to return only the methods available on `some_object` that AREN'T on typical objects, which is a very, very, very powerful learning/exploration tool.

For example,

    irb(main):003:0> PaypalService.methods - Service.methods
    => [:create_prepay_invoice, :build_client, :capture_invoice_funds, :get_order_info, :get_plan_price]

Side note: you can also call `.source_location` on any method to see exactly what file/line it's defined in (even in core ruby/rails methods). There's a lot of other inspection methods available to learn more about objects and what you can do with them, which IMO is a benefit over your latter example.