Only problem with the F diff is that your wheels won't fit under the guards unless you either shorten the diff or flare the guards a fair bit.
If you already have the hilux stuff then use it. Yes it is a lot heavier that the F diff but a lot of people are using them. I guess it all depends on what you want the car for. If it's straight line stuff then go for the G series if you want it for twisty roads then I would try and keep the unsprung weight down and use the F.