If you are happy with 1020 than why buy one? You must have a reason why you want to buy a 1520...
I have both 1020 and 1520, I love everything about the 1020 except the battery life - for my usage I can't last one full day without carrying an external battery - I'll be out of juice by 7pm. So I got a 1520 recently (last week as a matter of fact) for the incredible battery life. It's a bit big but it absolutely solved my battery/usage problem so I got my money's worth. Now 1020 is my backup phone.