God is perfect in every way. Therefore His original creation, including man, was perfect in every way. Yet the first man, with no sin nature, chose to sin. We call it a free will decision. At the Rapture, we will be perfected. Our sin nature will be gone. We will still have our free will. We will have the ability to sin yet we will choose not to sin. So how will we be different from Adam?
It’s true that Adam and Eve didn’t have a sin nature. They chose to sin after they were tempted directly by Satan. After the rapture we’ll no longer have a sin nature either. The first difference is that Satan will be locked up in the abyss, and nothing impure will ever be able to enter the New Jerusalem where we’ll live (Rev. 21:27).
Also, it can never be said that while God had enough love to save us, He didn’t have enough power to keep us. Our righteousness is equivalent to God’s (2 Cor. 5:21) and we’ve been made perfect forever (Hebrews 10:14). That’s why they call it Eternal Security, not just life long security.