Correct, it can be different for different people with different plans and needs.
One small correction there is that with Verizon the larger discount ($25/mo off) now applies to plans with 6 GB and above, and the smaller discount ($15/mo off) applies to plans below that, basically 4 GB and lower.
Yup...and you just supported my point about timing. These plans change often, so what might be most economical today may not be tomorrow.