For $3.5, Hetzner gives 2 vCPU, 4GB RAM, 40 GB SSD, and 10 TB of bandwidth.

Pretty oversold iirc, but then again, that's the same for Linode

Do you mean these are shared instances, and the stated resources are not actually available?

how much work should the GP do to migrate if Linode is good enough, to potentially save up to $1.50/month (or spend 50 cents more)?