Welcome Federal, I have both models so I made some pictures for you.
First off the sizes, Flash II 3,5'' (8.9cm) blade, 8'' (20.3cm) overall weight 3.1oz (88gr).
Trident 3.75'' (9.5cm) blade, 8.5'' (21.6cm) overall and it weights 3.6oz or a 102 grams.
The sizes are pretty close I guess, it's not a real big difference. The blade of the Trident is wider and has a 'bowie' shape. Both AUS 8 and zytel handle (which SOG provided with a good grip) but the Trident has of course a 'groove'. I don't use that but I've tried it and when you lock your blade it will do a good job on rope and fishing line and maybe your seatbelt.
Well lets place some pics to see the sizes.
Seems all pretty equal, I dont really prefer one blade shape, they both cut well. I think its more which blade shape do you like, and pick the one you like.
So I dont think one blade is better than the other but there are some things different. First off, I think that the arc lock on the Trident is better. Its a lot easier to close the blade. The piston lock on the Flash is harder to push down and it did hurt my thumb after a few times. So the Trident wins that one.
Then of course the opening of the blade, IMO the Flash wins here. The Flash opens more smoothly and the blade stays better in place. The Trident has a little more blade play than the Flash.
So if you want a easy folder for EDC then I would go for the Flash 2. Its a little lighter, easier to open and it just feels better for EDC work. However, if you think a Trident looks better then I would go for that one cause there is not much difference between those blades. The Trident is also good for EDC work although I think its a little too big. The Trident is better for the woods I guess, but the Trident can be a life saver if you need to cut your belt but I dont know if you think thats important.
So overall both knives are good but if I where you then I would just pick the one that you like most. As I said, the Flash feels more solid and opens better but the Trident has also some better things.
As for a EDC I would go for the Flash 2, a little smaller, opens better and feels better. Maybe the Trident feels better when you have really big hands, it has a extra grip on the blade to give you more feeling when you need to cut something with more precision.
The clips on these folders are both solid and you can lock both blades.
Also reed the lines that SOG wrote about these folders:
http://sogknives.com/store/TF-2.html
http://sogknives.com/store/FSA-8.html
Let us know if you have any more questions.