First, I don't believe the issue is Jesus being more interested in being "practical". While obedience is of utmost imprtance, so is our understanding of God. In fact, I don't believe there is a more practical "theological" issue than the Triune nature of the Godhead.
1. It allows me to understand redemption more fully-the Father choosing, the Son purchasing, and the Holy Spirit sealing and calling.
2. It allows me to understand the male-female roles more fully.
3. It allows me to understand that reality is essentially personal. The oneness guys can't say this. God was playing solitaire for all eternity, but the Trinity allows us to understand that God is fundamentally personal in himself. This is of utmost importance.
4. It allows me to understand the relationships of authority. One of the basic philosophical issues that the world can't answer is the "one and the many", but Christianity allows us to understand this from the outset.
5. It allows me to understand ethics in their appropriate role.
All in all, the Triune nature of the Godhead is essential for ALL Christian doctrine, and not some speculative issue. To act like it is a concept that we can't fully understand, so we will just wink at it is careless. I don't "fully" understand anything, but I do comprehend things partially. I am a finite analogy of God, so none of my thinking is exhaustive. Only God has that privilege.
No, we aren't looking at something from two different perspectives. I agree that a lot of knowledge is perspectival, but both camps understand what the other is saying and we disagree.
Stauros56 says, "It is rather sad that our trinity friends have so much animosity against their Oneness brethren and all because they cannot use any real scriptural evidence to suuport their theory." Hmmm, I like the, "I'll try to take this, animosity, from their hand, while I hit them with my own ('all because they...')." Well, I don't see it as having animosity toward you in and of itself. It is seeing your doctrine as heresy. Like all heresies, we oppose it, which in a strict sense is animosity, but not as animosity is typically used, i.e. an irrational enmity. The rest of his post is an underhanded way to try and take the high ground, i.e., if you disagree with me than you are simpley a judgmental, unsaved, antagonistic, etc., man.
Developing the shema in the NT is beyond the scope of this post, but study 1 Co. 8:6 with Dt. 6:4. Ahh, Trinitarian through and through.
Delighting in the fellowship of the Father, the Son, and the Holy Spirit.
For an excellent devotional that studies these elements see John Owen "Communion With God".
P.S. Yes, due read Piper on the Trinity, and his "mentor" Jonathan Edwards--his unpublished article on the Trinity found at jonathanedwards.com