If you wish to do extended travel, especially away from the supercharger network, the larger the battery the better.
The dual chargers are only used if you are charging on a HPWC that is set for amperages greater than 40A, or for some of the J1772 chargers (although almost all of those chargers are limited to 30A). If you do have access to those chargers, you will be very happy to have the dual chargers.
Other tips: Buy the CHAdeMO adapter. Buy all of the plugs adapters Tesla sells. Buy (or make) plug adapters that Tesla doesn't sell.
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I recently went on a 14000 mile road trip. I did not keep track of my actual charging experiences, but there were less than a dozen times that I was able to take advantage of my Tesla's dual chargers. Almost all of my charging was on Superchargers, CHAdeMO chargers, or on chargers that provided 40 amps or less--so the dual chargers were mainly superfluous.