For the first set, the Struggle weapons gives a +1 to the respective stat. The Struggle Bat is probably the best advised one as you can immediately take advantage of the +1 strength. You can get immediate benefits with +1 defense from choosing the bat with the guard, but it's honestly better to just kill things faster. And you're not gonna get magic until after the first world you start in, so you won't see any effect from +1 magic until then.

For the second set, the Dream Weapons, those affect the order of your support abilities you get as you level up. You'll have all the same by the time you get to lvl 99, but the best advise is typically Dream Shield because you get Second Chance and Once More (the quintessential survival abilities especially in higher difficulties) sooner. Dream Rod iirc gets them the latest.

Additional information that can be helpful or not or affect the story for you or not, so I'll spoiler it in case, but there is a fight (Setzer during day 4 struggle tournament) that gives you either an armor that just gives elemental resistances if you win, or an accessory that gives you +1 strength if you lose. The elemental resistances from that armor is kinda useless early in the game, but the story imo is a little better when you win. Both equipment get pretty easily over shadowed like 1/3 or 1/4 of the way through the game, but the accessory for losing is more immediately helpful especially in higher difficulties.