the large miner is 4x4 = 16 tiles, but only 50% faster than the medium miner which is 3x3 = 9 tiles, so replacing an ore patch with large miners decreases your ore/second, with no upside.

even accounting for the lane in the middle, two medium miners fit into 3x7 tiles for 5.71 ore/tile minute, and two large fit into 9x4 for 5.00 ore/tile minute.

the only stat that increases is mining area, which theoretically means you can place them further from the edge of a patch than mediums, but that's where the ore is first going to run out, so it's only useful if you want to spread miners sparsely, which you'd only want to do if they were expensive but powerful.