The theory that it could in fact be more favorable in BTC terms to exit is an interesting one. If a particular mint could be valued less, in theory one could be valued more.

Because of the smart contact module system in fedimint, there's a possibility that the functionality of modules on one mint but not another could push demand to be in that system. If it costs 200k to swap BTC in for Ecash on chain (mining fees) and there's an LN gateway willing to let you come in for 100k fee, in that case your 500k sat swap costs you 600k and netted the gateway (a user of the mint functioning as a swapping provider) an extra 100k profit. In the end, it saved you money.