Get the G5. It fixes some problems the G4 has.
The problems with the G4 don't happen to everyone, but they happen enough, and in competitions, too, that fixes for them have made it into WCA regulations where they're referred to as "common incidents".
The G4 power and reset buttons can easily be accidentally hit when simply trying to stop the timer, thereby resetting it or powering it off, resulting in a DNF. The fix is to tape or glue a rubber o-ring around the buttons or use a 3D printed part to protect them (I have links, if anyone wants them). One is by Speedstacks, the maker of the timer, so even they know about the problem.
G5 fixes that. Power and reset buttons are just a little bit harder to press, and you have to hold them down for a fraction of a second. No more accidents.
Another G4 problem is that the batteries can sometimes come loose inside the battery compartment and cause the timer to power off and/or reset. Fix is to fold a small piece of paper and stick it inside the battery compartment, between the batteries and the compartment door, to hold the batteries firmly in place, "padding" the batteries.
G5 fixes that, battery compartment door is tighter and firmly keeps the batteries in place.
Another G4 problem is where the cord plugs in if you want to use it with a display or with your computer. It's very, very easy to knock the cord out.
G5 fixes that, cord plugs in inside a slot under the timer now and can't be accidentally unplugged.
One thing with G4 that's not as much of a problem, but can still be inconvenient/annoying, is that the timer just sits on the buttons on the mat and slides sideways to hold it in place. It can still be accidentally slid sideways and knocked off the buttons. The G5 fixes that by actually snapping onto the buttons on the mat and requires effort to unsnap it.
Can't use a G5 on a G4 mat, only a G5 mat will work with a G5 timer. The G5 and G4 buttons on the mat are slightly different size and slightly different distance apart.
Doesn't matter that the G5 has 4 touch pads, because you put it into 2 pad mode and ignore the thumb pads. The thumb pads are only for cup stackers. WCA even shows how to completely disable 4 pad functionality, so the G5 can't accidentally be started in 4 pad mode. (I have a link to it, if anyone wants it.)
