For a Pokemon to be considered a strong pick in-game, it should be able to quickly OHKO opponents, learn strong moves through level-up and TMs, and be easy to train. As you'll see, the three Unovan starters were not created equally in these regards.
Serperior is the fastest starter and has balanced defenses, but its mediocre attacking stats often leave it just short of the KO. The highlights of its shallow movepool are Leaf Blade, Coil, and Giga Drain at Levels 32, 38, and 44 respectively; Serperior gets few options unless you're willing to grind Blue Shards for Aqua Tail and Dragon Pulse. It struggles against Roxie, Burgh, Elesa, and Skyla but does well into Clay and Marlon. It is fairly average everywhere else and is hindered by the weak defensive profile that comes with being a pure Grass type.
Serperior is overall the worst of the starters, though it's by no means the bottom of the barrel when it comes to Grass types.
Emboar is appealing thanks to its high Attack, especially coupled with Hammer Arm from the Move Relearner and Return from Floccesy Ranch. That said, Emboar's low defenses and dearth of strong STAB moves are cause for concern, particularly when its strongest Fire option — Flamethrower at Level 43 — comes off its weaker Special Attack. Emboar shines against Roxie, Burgh, and Colress, but struggles against Clay, Skyla, Marlon, and Caitlin. Its beefy HP makes it an above-average neutral matchup into most other important Trainers.
Emboar is fairly linear but a powerful force against many of the game's important fights. Take care with its low Speed when using it in battle.
Samurott has balanced attacking stats, reasonable HP, and mediocre defenses and Speed. These attributes make it difficult for Samurott to define itself at any one task, but this doesn't detract from its overall usefulness. Surf (HM) and Aqua Jet (Level 33) are its strongest STAB options and pair well with its diverse coverage options: Megahorn, Ice Beam, and Revenge are all high-value moves that give Samurott a way to hit most important Trainers. This makes it one of the best answers to Clay, the strongest starter against the Elite 4, and a powerful asset for random Trainers. Its weakest matchups are Burgh and Elesa and it struggles to stomach hits if it can't OHKO a foe.
Samurott is the most consistent — and therefore the strongest — starter. Though it's not as fast as Serperior and doesn't excel in certain fights like Emboar, its reliable nature and robust movepool make it useful from the moment you receive it to the moment you defeat Iris.
