I think your goal is to save money while managing the tax impact. I would prioritize using:
* expense ratio. This is the money you hope to save by switching to Vanguard. More expensive means you want it sold first.
* current value MINUS "cost basis": your taxable profit. When selling you will owe taxes, but there's no way around that. You either keep funds you don't like, or you sell them.
* how long the funds were held: if it's just under a year, it pays to wait. Median tax rate is 25% of gain for short-term (held 365 days or less), but 15% of gain for long-term (366 days or more).
I say prioritize because maybe selling will push you into a new tax bracket, or is too much gains for whatever reason. So aim to sell the most expensive funds first, with the lowest tax impact.