You're welcome, Ethan.
Here are links to the iFly spec pages for each device. They seem to confirm the only difference between the 2 is the screen brightness (and price):
740: https://www.iflygps.com/STORE/Product/flash-sale/ifly-740-premium-gps
740b: https://www.iflygps.com/STORE/Product/flash-sale/ifly-740b-gpsfs
Andre'