Class vs. Namespace as Singleton

I was looking across some code and I found an unusual technique to implement public singletons. I have never seen this code style before in any code.

Here's an example of generic singleton code:

Code:

---

class Test {
private:
        Test() {}
        Test(const Test&);
        Test& operator=(const Test&);
public:
        char mem[0xFFF];
        static Test& Instance() {
                static Test instance;
                return instance;
        }
        void DoStuff(int i) {
                mem[i] = i*2;
        }
};

---

and to access:

Code:

---

Test::Instance().DoStuff(5);
Test::Instance().mem[2] = 10;

---

And here's an example that does the same thing, just with namespaces.

Code:

---

namespace Test {
        char mem[0xFFF];
        void DoStuff(int i) {
                mem[i] = i*2;
        }
}

---

Code:

---

Test::DoStuff(5);
Test::mem[2] = 10;

---

I was wondering, what are the benefits and drawbacks of either technique? Why would someone choose to implement a singleton class if they want all attributes public? Is there a performance gain by using one of the techniques? And, what are your thoughts on using namespaces like this?

Thanks,
eros.