Assuming the Gtech is effectively a single speed and v brakes, my personal view is...v brakes have been around for eons and are quite capable when set up correctly, shouldnt be a big deal. No gears ?, again, no big deal unless you run out of battery, then ebikes tend to be very heavy and gears can make life tolerable with no motor power. Perhaps the Gtech is light, perhaps if the terrain is flat, gears aren't really a big deal either.
My Carrera / Suntour powered bike has been generally very good, plenty of oomph, a few too many of the inevitable cut outs the Suntour ststem seems to suffer from but then, it hasn't happened in ages on mine and when it does, it's just press the power button and away you go.
That's the only niggle, mines done nearly 3000 miles, battery is starting to lose mileage achievable now, it seems to need charging more often but that's probably true of most batteries unless to go up a price bracket.
In essesnse, the Carrera pluses..
Well made
Really good hydralic disc brakes.
Quite a meaty powerful motor.
Quite well priced if you get it on one of their specials (I paid £1k for mine over two years ago, normal price then was £1.2k)
Minuses.
Do suffer from occasional power dropouts, but just press the on button and away you go.
I gather the newer versions have a less robust battery charger connector.
Heavy, really quite heavy.
I've been really pleased with mine, no real regrets.