Yeah this is a tough one. I myself personally will go to the originating station just so that my group can sit together. For example, on the San Joaquin, I've Ubered to Jack London Station vs taking the Amtrak Thruway to Emeryville which is much cheaper, just so we could get group seating. Generally, if I'm up in SF on the San Joaquin, it is during a long holiday weekend so getting on sooner is important to grab the seat that we want.