IMO: Both will provide excellent protection. However, you're basically asking to compare the lightest mask out there with the heaviest.
Disclaimer: I do not have the F3 V2.
Personally, I'd go with the All Star mag. It's super light and super comfortable. The jaw pad is really comfortable in any weather. I really like the idea of the plastic plate in the bottom pad to help disperse the energy of an impact. The top pad is just a regular LUC pad. The sightlines out of the mask are just okay. The bars are more like blades, so they're really thin but longer than your typical mask. IMO, it takes a game or two to get used to the view out of this mask. That said, I really like the way it looks and you would be in good hands with this mask.
The F3 will provide excellent protection as well, possibly better than the All Star mag. Not to say that the All Star doesn't provide protection, but F3 is widely considered some of the most protective equipment you can buy (except the CP, YMMV). The F3 is heavy. Someone is going to reply to that and disagree, but it is a heavy mask. That said, it's designed to be worn tight. This may or may not be comfortable to you, and you may need to practice taking it off without taking your hat off as well. I've also been told the visibility out of the F3 is a little different because you have that floating cage that sits so far away from your face. But this mask is very protective and would be a good choice as well.
At the end of the day, as with anything, it's all personal preference. Both masks feature cutting edge technology and both are very very good options. The All-Star will be lighter, probably more comfortable, and protective (and looks better ). The F3 will be heavier, worn tight, and very protective. You won't go wrong either way. Personally, I'd get the magnesium.
@JimKirk will tell you to buy both on Ump-Attire and return whichever one you don't like at their expense! @MadMax will tell you the same thing I told you, but 10x longer.
Good luck and happy umpiring!