Resigning Before 1 Year Mark

Background: Prior to starting my full-time IB role, I was under the impression that I would be joining the same team I interned with the previous summer. I was highly motivated to begin, as the team operated in a vertical I was genuinely interested in, had strong deal flow and was led by senior bankers from whom I expected to learn a great deal. Although the firm was located in a less desirable city (e.g., Detroit, St. Louis, Pittsburgh), I was comfortable with this trade-off given the team and opportunity. Upon starting full-time, however, I was reassigned to a different group in a less desirable vertical (e.g., tech to T&L) with materially less deal flow. The senior leadership on this team is largely disengaged from junior banker development (not saying this should be their first priority, but rather that they simply do not care) and is more focused on minimizing their own personal workload. During my internship, I had heard unfavorable feedback about this group and was relieved at the time that I had not been placed there; unfortunately, I am now. Following this reassignment, I reconnected with contacts at other firms and subsequently received an offer to join a stronger platform on a more attractive coverage team (e.g., healthcare, consumer) at a higher-quality bank located in a Tier 1 city (e.g., New York, San Francisco).

Given this context, would leaving my current role prior to the one-year mark be viewed negatively from a long-term career perspective? Additionally, if I choose to accept the offer, what are best practices for resigning in a professional manner?