Tatsu arrived on Earth older than the canonical Goku, with a birth power level of 35. Over the past year, his primal, instinctual training has pushed his strength far beyond that of a typical low-class Saiyan warrior.
Initial strength: At three years old, his birth power level of 35 would have already put him far ahead of the canonical Goku at the same age. He was a brute-force fighter, relying on aggression.
Self-inflicted "Zenkai" boosts: Tatsu has repeatedly pushed himself past his physical limits through high-altitude and underwater training. Each time he recovered, he would have received a "Zenkai" boost, a Saiyan ability that drastically increases a warrior's power after recovering from a near-fatal injury. His brutal self-conditioning is essentially a constant, low-level Zenkai training.
Battle Meditation: His accidental discovery of a battle-focused meditation has refined his ki control and natural fighting instincts, making him a more focused and efficient combatant.
Current estimate: At this point, Tatsu's power level would likely fall in the range of 500 to 1,000. He would be a formidable force, roughly comparable to a Saibaman or even Raditz, but without the benefit of a Scouter.Goku's estimated power levelGoku, with his gentle Earth upbringing and head injury, has followed a different, gentler path to power. He is younger, less aggressive, and primarily influenced by Gohan's compassionate teachings.
Starting low, growing steady: Goku's power level at birth was 2. Over the past year, he has been training under Gohan's careful guidance, but his training emphasizes discipline and control over raw aggression.
Unconventional training: Goku's growth has come from unconventional training, such as "protecting the rock" or "fighting the water" with Tatsu. He has not experienced the same level of self-inflicted pain and Zenkai boosts.
Infectious energy: His growth is more a function of his infectious nature and his willingness to learn. His playful "fighting" in the lake with Tatsu and his precocious smiles are a different kind of strength, one based on joy rather than aggression.
Current estimate: At this point, a young Goku would likely have a power level in the range of 300 to 400. He would be a decent fighter, stronger than the average human, but not yet at the level of a full-fledged warrior.ConclusionWhen comparing the two, Tatsu would be the more powerful and dangerous of the two in a straight fight, driven by his natural Saiyan instincts and brutal training. Goku, though weaker, is the more adaptable and kind-hearted, with a knack for turning a brutal challenge into a game. The true test for both will be how they continue to grow and develop, shaping their Saiyan powers with their uniquely different Earth upbringings.