Difference in passing * vs & to a constructor in C++

Question

Dear friends,
Could you please:

• exlain the difference in the following cases;
• tell what is the better choice of using.

Thanks in advance.

class OtherClass {
public:
    void otherFunc() {};
};

//Case 1: passing an object argument with '&'
class SomeClass {
private:
    OtherClass& _other;
public:
    SomeClass(OtherClass& o)
        : _other(o)
    {}
    void aFunc() {
        _other.otherFunc();
    }
};

//Case 2: passing an object argument with '*'
class NewClass {
private:
    OtherClass* _other;
public:
    NewClass(OtherClass* o)
        : _other(o)
    {}
    void aFunc() {
        _other->otherFunc();
    }
};