I've been studying Vaisnava doctrine, so I have some familiarity with the distinctions you're making.
The problem from a Christian p.o.v. is that as far as we're concerned, Christ is I guess what you would call the highest, eternal "expansion" of God - the Logos, which in Greek means the word/rationale of God. He has all of the "opulences" of His Father, and is in fact the agency by which all things which are have come into being.
Another important distinction, is that while Christianity (at least in it's Orthodox form, as in "Eastern" Orthodox) teaches on the the Divine Energies and that they are eternal, a distinction is made between these energies, God as He is, and the creation. My understanding is that Vaisnavism teaches that all things are fundamentally a part of God, and that souls are eternal (having no beginning, and obviously no end) and are qualitatively (if not quantitatively) equal to the Bhagavan/"Supreme Personality". On the otherhand, Orthodox Christianity teaches that all things (including souls, whether they be those of men or the different classes of angelic spirits) are created, they had a begining, and if they have no end, this will be solely by the will of God. Things continue in existance by the Divine Energies, and the closer they are to God the more they manifest His Personal qualities, but these are distinct from that which is sustained by them and bathed in them.
This is why ultimatly the Christian concept of "Incarnation" and the Vedic idea of "avatara", while similar in some important respects, are not indentical. I've seen Krishna devotees here mock the Christian ideal, typically because the Scriptures clearly outline the materiality of Christ's human nature, that He was besides being Divine, truly a man. As far as Christians are concerned however, God "as He is", is uncircumscribed - He is above the categorizations of the temporal world, which would include such things as location, shape, size, etc. Hence why, if God were to take on a visible form, it involves some kind of condescension on His part - whether it be the shaping of Divine energies in a manner perceptable to the senses (this is perhaps close to the Vaisnava idea of avatara - for example, the theophanies talked about in the Old Testament), OR in the case of Christ, the assumption of human nature. For Christians the latter (assumption of humanity/incarnation) has a significance which is overlooked here - namely the sanctification/elevation of humanity. Christ, as a man, overcomes the world, by a humanity infused with Divinity. This in ancient Christian dogma, is the heart of the ascetic struggle/podvig of salvation.
Unfortunately, people will keep talking past each other, and will be incapable of engaging in a meaningful debate of ideas, if we're not understanding what the other actually believes.