In other words, Jesus could take the filth in our hearts, cleanse it, take it upon himself and get rid of it - granting us a pure heart and eternal life.Romans 6:23 "For the wages of sin is death, but the gift of God is eternal life in Christ Jesus our Lord."
I think the Buddha had a similar aim in that the application of his teachings alone could purify the heart, release it from the filth and the fermentations in there - granting us a place in the Deathless.
The difference is obviously that Jesus is offering to do this FOR us. The Buddha is teaching us how to do this for OURSELVES.
This may also be an indicator of just what kind of short life Jesus lived compared to the long life and extensive teachings of the Buddha.
I wouldn’t be surprised if there is little to no difference between the Kingdom of Heaven and Nibanna. I would also not be shocked if “the Deathless” and “eternal life” are equivalent.
DN 1 - describes the idea of life in a Brahma heaven. But I don’t see Christianity as being a “union” with the Great Being. It is more about forgiveness of sins and purification so that one may find a happy destination after death.