Most efficient way to level up and train Pokemon traded from NPCs
I know that when you trade a Pokemon with an NPC, the Pokemon they give you is at the same level as the one that you trade with them, but is there any incentive for trading really low level Pokemon with the traders? I also know that if you catch a specific wild Pokemon at a high level, its stats will tend to be worse than those of that same Pokemon if you caught it at a low level in the wild, and leveled up to that high level. So, if you catch a lvl2 Pidgey in Route 1, and grind it up to lvl19, it’ll be stronger than a lvl19 Pidgey that you caught in Route 7.
Is the same thing true for Pokemon that you gain from trades?
I’m asking this because I’m early on into a playthrough of Pokemon Red. (US) I have two Spearows. One of them is at level 10, and the other is at level 15. I don’t know which of them I should trade with the man in Vermillion City in order to get the Farfetch’d. If I trade in the lvl10 Spearow, and grind the Farfetch’d from lvl10 all the way to lvl15, will its stats be any higher, (or lower,) than if I just trade my lvl15 Spearow for a lvl15 Farfetch’d? Thanks.