In a 10-team fantasy league, every roster seems that much better since there are two fewer players drafted each round than in a 12-teamer. The trickle-down effect is that the scoring differentials at each position interval (i.e. starting QB1s range from QB1 to QB10, or RB2s range from RB11 to RB20) are smaller.
Point being, in a 12-team league, the advantage gained from having the assumed TE1, Travis Kelce, is a larger advantage because the "worst" starting TE, TE12 Mike Gesicki, casts a wider range than the "worst" starting TE in a 10-teamer, TE10 Dawson Knox.