Some people may think that the pain of a heartbreak is less severe if a relationship lasts only for a very short time; some believe that if you're not very much into the relationship, the pain of a heartbreak will be bearable. But is it?
Every time you get into a relationship, you risk showing the most vulnerable part of yourself to another person. You actually choose to take out your heart and try to connect it with another person's heart. Imagine two connected hearts being torn apart, of course it will hurt. Even though you may not be super into the relationship, you did connect a part of your heart with the other person's. When the bonding is broken, tearing the connected part of the hearts is of course still a painful experience, same painful.
Time isn't a factor that causes a heartbreak more or less hurtful either. It does take time for a relationship to grow, and it's likely that the two hearts get more connected as time passes. But there're also relationships in which the passion and feelings fade as time goes by, and on the other hand some people get really really connected within a very short time.
The level of how much you're into the relationship, however, may affect how fast you recover from the pain. The more connected the hearts, the bigger the wound will be left when they're torn apart; and so it'll probably take a longer time for the wound to heal.
So I'd say, all heartbreaks hurt the same. If you get into a relationship, expect that you may experience another heartbreak which can be as painful as your last one. (I'm not saying that you should not have faith in your relationships, it's just preparing for the worse while hoping for the best!)
Despite what I've said, it doesn't mean that you should not let yourself be into a relationship much in order to avoid the long heart-healing process. Every heartbreak is a lesson in life. You'll learn something that will stay with you for the rest of your life. A heartbreak also means that you have experienced love. And life is so short that it's better to have experienced it than regret never having been in love.
More great stuff to read:
How It's Like To Be A Person Who Feels So Deeply
Why You Still Choose To Fall Into An Uncommitted Relationship