Ссылки vs указатели - в чем разница?

#include <iostream>
#include <vector>
#include <algorithm>
#include <ctime>
using namespace std;
 
struct A
{
int n;
static bool isExpressed;
static int cnt;
static int del;
static const int N=10000;
double myArray[N];
 
void arrInit()
{
for(int i=0; i<N; i++)
myArray[i]=i;
}
void arrInit(const double *a)
{
for(int i=0; i<N; i++)
myArray[i]=a[i];
}
 
A()
{
cnt++;
n=0;
arrInit();
if(isExpressed) cout<<"A()"<<cnt<<endl;
}
 
A(const int a)
{
cnt++;
n=a;
arrInit();
if(isExpressed)cout<<"A(const int)"<<cnt<<endl;
}
 
A(const A &a)
{
cnt++;
n=a.n;
arrInit(a.myArray);
if(isExpressed)cout<<"A(const A&)"<<cnt<<endl;
}
~A(){
    del++;
    if(isExpressed)cout<<"~A()"<<del<<endl;
}
int operator<(A &rhs)
{
return n<rhs.n;
}
static int compireByPtr(A*lhs, A* rhs)
{
return *lhs<*rhs;
}
};
int A::cnt=0;
int A::del=0;
bool A::isExpressed=true;
int  main(void)
{
    
const int size=1000;
A *arr = new A[size];
srand((unsigned)time(NULL));
for(int i=0;i<size;i++){
    arr[i].n=rand()%(size-1);
}
vector<A> first;
for(int i=0;i<size;i++)first.push_back(arr[i]);
for(int i=0;i<size;i++)cout<<first[i].n<<" ";
cout<<endl;
 
A::isExpressed =false;
 
clock_t tBegFirst=clock();
sort(first.begin(), first.end());
clock_t  tEndFirst=clock ();
clock_t spanF= tEndFirst-tBegFirst;
cout<<"first elapsed "<<spanF<<endl;
 
for(int i=0;i<size;i++)cout<<first[i].n<<" ";
cout<<endl;
 
vector<A*> second;
for(int i=0;i<size;i++)
    second.push_back(&arr[i]);
 
clock_t tBegSecond=clock();
sort(second.begin(), second.end(),A::compireByPtr);
clock_t tEndSecond=clock();
clock_t spanS=tEndSecond-tBegSecond;
cout<<"second elapsed "<<spanS<<endl;
for(int i=0;i<size;i++)cout<<second[i]->n<<" ";
cout<<"\nfirst processing takes "<<(float)spanF/spanS<<" times more time than second"<<endl;
cout << endl;
    system("pause");
    return 0;
}