Really, it's a system where every choice is viable. There are the weapons with generally good Attack and Magic, some specialize in either and then a lot of weapons have supbar Attack and Magic but make up for it with a unique auto-ability.

Vanille really does best with the Belladonna Wand, in my experience. The additional Saboteur capabilities can really come in handy at times.

Sazh I went with the Deneb Duellers for the most part. Eventually I went over to the Pleiades/Hyades when I farmed Adamantoises but my main weapons were still the Deneb Duellers.

For Lightning I just invested in her standard weapon. I didn't think any of the other auto-abilities were worth the loss of power though it seems like the ATB Charge on Hit weapon is pretty damn good. Can't say I ever came to regret my choice though.

With Hope I think it was the Hawkeye I ended up going with though I can't remember what it did. Also forgot what Snow had, I rarely used him when I had a choice. Fang, finally, I went with the Taming Pole as soon as I got it. Stagger Lock isn't a problem as long as you have at least one character without it and that weapon is really damn strong. I heard the Quick Stagger (Lightning's Lion Heart) + 2x Stagger Lock combo is very effective but in the end, you can beat any enemy in the game with any weapon. The benefits of a weapon will always shine in some situations, not so much in others.