Last year:
// connect at 115200 so we can read the GPS fast enough and echo without dropping chars
Serial.begin(115200);Now:
gps_port.begin(9600);Are they two different things?
Yes. Serial is for printing debug messages to the Serial Monitor window (you can pick any baud rate, as long the Serial.begin number matches the choice in the Serial Monitor window). gps_port is for reading characters from the GPS device (usually 9600, but you can send commands to change its baud rate).
Other GPS libraries (and their examples) do not coordinate the sketch with the GPS quiet time. It is very common for those sketches to print too much information, use delay, or test if just one GPS field has updated. This causes them to lose GPS characters.
Your first sketch used Adafruit_GPS. It tries to work around the problem by printingreallyfast (to Serial @ 115200), in the hopes that the printing will complete before the sketch loses GPS characters. It doesn't always work, especially when users modify their example. :-/
Since you are using the correct loop structure (as encouraged by the NeoGPS examples), you do not have to worry about the Serial baud rate. You don't even print debug messages, so there's no reason to start the Serial port. This saves some RAM and program space, too.
BTW, you don't need these includes for the Pro Trinket:
#include <TinyWireM.h>
#include <USI_TWI_Master.h>
Cheers,
/dev