GPS Data Logger Software - BT747

I purchased a Photomate (or iBlue?) 887 logger about a year ago because it's very small and light and I use it to track my cats as they travel around the neighborhood.

I *NEVER* see any reference to the 887 on any of these GPS websites or forums.  It's always the BT747.  But I use the BT747 software to download the data from my 887 and configure the device.

Can someone explain the difference between the 747 and 887?