Final answer:
For a new credit card without historical data, U+ Bank should use an adaptive model to accommodate live data for personalization on their customer web portal.
Step-by-step explanation:
When introducing a new credit card with no historical customer behavior available, U+ Bank should opt for an adaptive model. Unlike predictive models that require historical data to make informed predictions, an adaptive model is designed to learn and adjust in real-time as customer interactions occur. This allows the bank to tailor their offerings on the customer's personalized web portal as new data comes in, leading to more effective and personalized customer experiences.