Export for Print - Full size VS Custom Inches

Hello Lightroom Fam,

I would like everyones opinion on what is better for exporting an edited photo for printing. The printing company I am using just takes .JPG at the moment and is ok for my current endeavors. 

When exporting , in the dimensions drop down,  should I choose the Full size option or choose the custom inches option. I am aware that exporting the full size option is a larger file size and has a 240 dpi in export. When choosing the custom inches the file size will vary depedning on the size of the orint ordered and I can choose 300 DPI on export.

Which do you think will harbor better results when exporting for printing. My printing sizes are from 11"x14" up to 24"x36"

Part of what has me thinking about this so in depth is that usually a larger file size equals more information and more information equals better quality. Any help and professional opinoons are very uch appreciated.