Read what dmrangerpk replied to me. Especially this part:
SL - In order to sustain SL off 2 stables this would cost 140f/24s or 5.83 f/s, at 0.32f/s this requires ~19 farmers to sustain (wiki gather rate used as source). Goldwise its 80/24 or 3.33g/s at 0.42g/s ~8 miners (gather rate includes the first mining tech)
Knight - 2 stables aswell, 120/30 or 4f/s + 150/30 or 5g/s This comes down to ~13 farmers and ~12 miners.
On top of the fact that SL cost 27 vs 25 vills to sustain there is also the upfront cost. Villcost aside gold has no upfront cost, but the additional farms cost an additional 360 wood.
Long-term food is definitely much better, but if your goal is to get an early lead and force fights then knights are easier to sustain and a much more well-rounded unit.