The one that makes all workers cost 1 less is a first age building. You can profit it from it on all 4 feeding rounds if you build it early enough. The 3 workers free building is a second age building and would be good for 2 feeding rounds max.
If you start with the tile that gives you an extra worker and get more extra workers early that 1 less farm would be extremely valuable.
If you start with the tile that gives you an extra worker and get more extra workers early that 1 less farm would be extremely valuable.