The point of difference is the precise definition of sin, because I think everyone believes Jesus was to the sinless side of that point by an infinitesimal amount.
Is this really what you meant to say? "Infinitesimal" means by an amount infinitely small, which is to say, an amount so small that no smaller amount could be found.
So, for those who believe that inherent propensities to sin do not count as sin, they believe that Jesus had those propensities.
As the SOP uses the word "propensities," actually participation in sin is implied, so I don't think anyone on either side of the question believes that Christ had these propensities. For example, the Baker letter states:
Be careful, exceedingly careful as to how you dwell upon the human nature of Christ. Do not set Him before the people as a man with the propensities of sin.
There are those who believe selfishness is not sin, as long as you do not perform selfish acts. Such people can believe that Jesus had selfishness, but He did not act on them.
I don't know anyone who believes this either, that is, that Jesus Christ had selfishness. Keeping with the usage the SOP uses with an analagous term, "sinlessness," one could not say that Christ "had" selfishness, as this would imply He was selfish.
To explain further, from the SOP we read:
We should have no misgivings in regard to the perfect sinlessness of the human nature of Christ. (5 SDABC 1131)
She also wrote:
He took upon His sinless nature our sinful nature, that He might know how to succor those that are tempted. (MM 181)
So she wrote that Christ took our sinful nature (she never says Christ took a sinless human nature), but we should have no misgivings in regard to the sinlessness of that sinful human nature. Now that sounds like an oxymoron, or a contradiction, but it's not, as one considers how she uses these terms.
In taking upon Himself man's nature in its fallen condition, Christ did not in the least participate in its sin. He was subject to the infirmities and weaknesses by which man is encompassed, "that it might be fulfilled which was spoken by Esaias the prophet, saying, Himself took our infirmities, and bare our sicknesses." He was touched with the feeling of our infirmities, and was in all points tempted like as we are. (5 SDABC 1131)
Christ took our nature in its fallen condition, but did not least
participate in its sin. Since she also writes
[T]he flesh of itself cannot act contrary to the will of God.(AH 127)
it seems evident that what she means is that Christ, while taking fallen, or sinful, human nature never acted contrary to the will of God, even though He took such a nature.
Getting back to how she uses the word "sinlessness," she uses that in relation to actual participation in sin. Christ never participated in sin. Again:
His life of sinlessness, lived on this earth in human nature, is a complete refutation of Satan's charge against the character of God. (ST 12/20/05)
The following statement makes it clear that the sinless being spoken of is not in regards to the human nature we inherit:
Those only who through faith in Christ obey all of God's commandments will reach the condition of sinlessness in which Adam lived before his transgression. (MS 122, 1901)
There are those who by faith in Christ will reach the condition of sinlessness in which Adam lived before his transgression, but their sinful, inherited human nature will not be changed, until corruption is changed into incorruption at Christ's Second Coming.
So we see that the "ness" at the end of the word implies participation in acts of righteousness, when attached to "sinless," and is not a static characteristic of an inherited nature. Similarly "selfishness" would imply, at least in terms of how Ellen White wrote, a participation in selfish acts, which, of course, we could not ascribe to Christ. So one could not say, in harmony with EGW's usage, that Christ "had selfishness," but I suppose one could say that Christ took a "selfish human nature," since she used terms like "sinful" "fallen" and "degraded" in reference to the human nature which Christ took, or inherited.
It may be that someone (like Denis Priebe has been accused of saying) may believe that Christ "had selfishness," but I would disagree with this statement, at least in terms of how EGW uses similar language, and this statement, which is just a statement by one human being, is by no means typical of those who believe the position that our church articulated regarding the human nature of Christ until at least 1947 was correct.
I believe one of the most significant things Ellen White wrote on this subject is the following:
Letters have been coming in to me, affirming that Christ could not have had the same nature as man, for if He had, He would have fallen under similar temptations. If He did not have man's nature, He could not be our example. If He was not a partaker of our nature, He could not have been tempted as man has been. If it were not possible for Him to yield to temptation, He could not be our helper. It was a solemn reality that Christ came to fight the battles as man, in man's behalf. His temptation and victory tell us that humanity must copy the Pattern; man must become a partaker of the divine nature. (5 SDABC 1082)
What makes this statement so significant is its context. She had been preaching with Jones and Waggoner, the three of them preaching righteousness by faith together, and questions had been coming up in regards to what was being taught regarding Christ's human nature. Christ's human nature was a part of the 1888 message which Jones and Waggoner taught, and here we see EGW preaching along with them and defending the position which they presented.
I don't think the question of the precise meaning of sin is so much the question as so much the nature of Christ's flesh, in particular, in relation to Christ's temptations. For example, I myself would not define sin as being limited to the volitional definition, yet I believe that Christ took our fallen, sinful human nature.
In regards to temptation, our heredity enters into our temptation. We have tendencies to sin which were inherited from our ancestors. Did Christ share in such a heredity as we have? Did he inherit tendencies to sin from His ancestors? Did His heredity enter into His temptations as our heredity enters into ours? This is where I think the real question lies.