Just in case I get carried away with what I'll be saying in this Lead Tidbit, let me answer the question up front: My answer is BOTH. Now let's take a couple of steps back.
I knew a guy, a Jew, a lawyer, who was not observant of Torah and Mitzvot. Nothing uncommon about that, but his reason for not following the Torah was unusual. He told me once that mitzvot were important for me, because I needed them to build a relationship with G-d. But he didn't need mitzvot because he was one with G-d.
He had such a close relationship with G-d that mitzvot were rendered obsolete. Many, many hours that I spent talking with him, arguing with him, were wasted (probably) on him... but not on me. The experience helped sharpen my understanding and appreciation of Torah and Mitzvot. Judaism is not a do-it-yourself religion.
Nor can we take inspiration from Old Blue Eyes singing about "doing it my way". Yes, there is some flexibility and variations in what we do, but always within halachic guidelines. What I'm warming up to say addresses the main theme of Vayikra - KOR- BANOT. But it applies to many, if not all, of the mitzvot in the Torah.
This includes the positives and the prohibitions. Simply put, a KORBAN without sincere T'shuva is less than worthless. It is a mockery of G-d and His Torah. It seems that many of our ancestors failed to get the point and were repeatedly castigated by G-d via the Nevi'im about the worthlessness of their insincere sacrifices.
On the other hand, if the experience of a person bringing a Korban was supposed to sensitize him; if it was supposed to help him on the path of repentance - then what about a person who can do real, complete T'shuva without korbanot? Does he need a korban?
The difficulty that we have in answering that question correctly is a result of centuries of not having a Beit HaMikdash and its Avoda coupled with the feeling that we manage to succeed at T'shuva without the help. That does not mean that we have permanently replaced our bulls with our lips (prayer). Prayer has always been there, regardless of whether we have a Mikdash or not. It's just that prayer and T'shuva have been doing double duty since the Churban. Korbanot as a means to achieve a better quality relationship with G-d is only one of the reasons for korbanot.
They, like all mitzvot, are the commands of the Infinite G-d and that makes them ends in and of themselves. To put it differently, in the time of the Beit HaMikdash - past and future - if a person violates the Shabbat inadvertently, he can be forgiven by G-d only with T'shuva and a Korban Chatat. Neither on its own will suffice.