Beep. Sorry I am late, and I am sure everyone has updated their views, but if I may add my input:
Beam: standard works well for all situations. Fast charge beam: weaker, can't be angled as steep, charges slower, shorter range, doesn't bounce nor pass through opponents (big minus for team battles). I can't see anybody ever needing this one. Theoretically you can spam, but I personally think it has too much startup and endlag to really use this short ranged laser. Wide beam: great speed and angles of beam, charges fast, lower damage. I feel this one has a lot of potential if you can master the angles fired. You can snipe opponents far above or below the stage
Side b: Again, standard works well for most people. Reflector arm is my favorite because the extra reflecting time and reflecting power is a Godsend against many characters, and like Byxis said, it is good at pushing away characters, which is useful near the edge/offstage. Backwards arm: It seems useless compared to the other two
Up B: Again, like Byxis said, standard was nerfed so HSB can even exist. High speed burner: universally loved, can get back onstage faster than most. Can follow up easier on Dthrow This should be the new standard. Robo Rocket: You might be able to use this to escape combos and can meteor, but it is not worth it since you still have to land to recharge it
Down B: Standard gyro is great, most of us are probably used to it. Slip Gyro: Awesome tricks are possible if you can keep this near your opponent so they stay trippin, though it does slightly less damage. Fire Gyro: my favorite due to the higher damage, but the endlag is punishable at close range so I might go back to slip gyro
Beep. Boop!