Welcome to Aximsite!
You have several GPS options with your X30H:
1. BT - NO SUBSCRIPTION COST; wireless; can be used with other devices with BT connectivity; leaves SD slot open for maps; requires you carry two devices; seems to be the most popular for X30H
2. Serial - connects to the serial port via cable; only works with the device for which it was designed; leaves SD slot open for maps
3. SD - fits into SD slot meaning you are carrying just one device; SD slot cannot be used for maps
For more info, consult Jake's GPS guide
here