In general I've seen that T3 (and now T4) instances on EC2 are both more cost-effective and powerful than T2 (obviously under the assumption it's the same type e.g medium).
The only exception I've seen for this is when using Windows AMIs it might be more cost-effective to use a T2. But looking specifically at AWS's on-demand pricing this doesn't appear to be true? https://aws.amazon.com/ec2/pricing/on-demand/
Is this actually true still? If so, what am I missing?