Great question! I started with an Uno and I believe the SD card reader stomped on me. So my baseline was software serial.
Also - I'm VERY new to Arduino (less than a week in my hands) so am unfortunately obliviously unaware of the capabilities.
So looks like I should use attachInterrupt() and add a service routine to handle the serial input from the GPS? Sorry for fumbling around - yet a bit more guidance (aka code I could copy) would help me move forward and learn fast I think! Thanks for your question and any further help!