Is being "sinless" the same as "being perfect"?

I will answer your question of whether being “sinless” is the same as “being perfect” first without dealing with how you further expanded it. I also assume you are taking the English meaning of the word perfect, and not the greek one. This distinction has already been mentioned on other answers.

I think the answer is "no" based on the following examples:

1. Adam before he became a sinner:

Although he did not commit any sin until he took and ate from the wrong tree, the Bible tells us that he was made "upright": Ecc. 7.29 (NASB, KJV, ASV):

29 Behold, I have found only this, that God made men upright, but they have sought out many devices."

We also see Adam not taking any initiative or decisions of his own until becoming a sinner. Until then, God was leading and he was following. On the other hand, after he became a sinner, he was immediately filled with his own initiative - he began to think he was wise (as we all do today because we were born into his race). After all, he had just eaten from the tree of the knowledge of advantages and disadvantages and was now in full control of the course of his life from his perspective.

So for a season he was sinless but was never perfect.

2. Lucifer before iniquity was found in him:

Ezekiel 28.15-17 plainly states (KJV):

15 Thou wast perfect in thy ways from the day that thou wast created, till iniquity was found in thee. 16 By the multitude of thy merchandise they have filled the midst of thee with violence, and thou hast sinned: therefore I will cast thee as profane out of the mountain of God: and I will destroy thee, O covering cherub, from the midst of the stones of fire. 17 Thine heart was lifted up because of thy beauty, thou hast corrupted thy wisdom by reason of thy brightness: I will cast thee to the ground, I will lay thee before kings, that they may behold thee.

It was because of his perfection that he sinned. Even displaying perfect attitude/dids he couldn't handle being perfect and sinned. His heart was lifted up and he sinned.

So perfect behaviour does not guarantee one will remain sinless.

I would welcome any discussion on the Hebrew term "perfect" used in this passage. But the context seems to indicate it could mean the same as in English.

So no, sinless and perfect seem not to be the same thing.

Now, in light of your question (the rest of it) about how God really wants us to be, consider the types of sinlessness of God the Father, the Son, and the Holy Spirit, and God's ultimate purpose for our lives being (Rom 8.29):

to be conformed to the image of his Son, that he might be the firstborn among many brethren:

A. God the Father:

"Uncorruptible" "Creator, who is blessed for ever. Amen." - Rom 1.23,25 and the One that "cannot be tempted with evil" - Jas 1.13. and also Jas 1.17 reads (KJV):

17 Every good gift and every perfect gift is from above, and cometh down from the Father of lights, with whom is no variableness, neither shadow of turning.

He is the only One righteous and no righteousness can be generated apart from Him.

B. God the Son:

Instead of a self-generated righteousness, he always did what the righteous One, the Father, told/revealed him to do. Contrast: Joh 5.30,31 (NASB):

30 "I can do nothing on My own initiative. As I hear, I judge; and My judgment is just, because I do not seek My own will, but the will of Him who sent Me. 31 "If I alone testify about Myself, My testimony is not true.

He did what the Father would initiate, to the fullest level:

9 Jesus said to him, "Have I been so long with you, and yet you have not come to know Me, Philip? He who has seen Me has seen the Father; how can you say, 'Show us the Father'? 10 Do you not believe that I am in the Father, and the Father is in Me? The words that I say to you I do not speak on My own initiative, but the Father abiding in Me does His works.

C. God the Holy Spirit:

Sinless and perfect. In the likeness of God the Son, God the Holy Spirit also acts out of the Father's initiative. Not his own: Joh 16.13-15 (NASB):

13 But when He, the Spirit of truth, comes, He will guide you into all the truth; for He will not speak on His own initiative, but whatever He hears, He will speak; and He will disclose to you what is to come. 14 He will glorify Me, for He will take of Mine and will disclose it to you. 15 All things that the Father has are Mine; therefore I said that He takes of Mine and will disclose it to you.

The type of righteousness displayed and lived by Jesus is the (realizable) righteousness God wants us believers to receive and experience (never generate) in being each and every day more and more conformed with the image of his Son through a believer experiencing his identification with Jesus in death, burial, and resurrection (Romans 6.1-14, specifically 6.11-13).

THAT kind of living is to be guided by the Holy Spirit and being under grace and not being under law.

Nonetheless, the Christian life is not one of sinless perfection, since we constantly battle our flesh that tries to make us go back and live and walk like Adam did, in sin and death, we deciding what to do next and taking our own initiative.

I hope that helps!

You can have a house that's halfway through being built. And the work that's done so far can be flawless, with no problems anywhere, but it's still not a perfect house.

Or, likewise, have a look at Adam and Eve. They were created without sin, but when temptation came along, they chose to transgress God's commandments. Jesus, on the other hand, was also without sin, but he stayed that way even though he was tempted in all points, as we are..

This shows the difference between sinlessness and perfection: perfection implies a state of completeness, in which you no longer commit sin because you've matured beyond the point of yielding to temptation.

Jesus's atonement can take away our sins, making up for past wrongdoings in a way that we are incapable of. But when he commands us to be perfect, that calls for effort on our parts as well, to strive to live the Gospel, to work at improving ourselves until it becomes part of our nature.

Everyone has some sins that they just don't understand. Even if they can see how it might tempt some people, the idea of choosing to do it themselves just feels foreign to them. (Meanwhile, everyone has other sins that just feel natural and normal to them.) My understanding of perfection is that, when our faith and humility, repentance and obedience lead us to the point where every sin feels that foreign to us--which will most likely not be during this life--that that's the point at which the perfection that Christ commanded of us has been reached.