Is weaker only on written statistic, not on real, if u make math a sec:
Electric mining drill(IR):
Drill size 5x5 = 25
Mining area 9x9 = 81 tiles
Mining speed = 1.25/s
Mining speed x tile = 0,015/s
Mining speed x coverage = 0.05/s
Electric mining drill MK2(K):
Drill size 3x3 = 9
Mining area 6x6 = 36 tiles
Mining speed = 1/s
Mining speed x tile = 0,027/s
Mining speed x coverage = 0.11/s
Efficency for tile is +0,012, and 0.06/s for coverage(double space for mining drills!), for don't make useless IR mining drills Krastorio drills give the possibility of better site coverage,
anyway Advanced mining drill(IR) is the MK4 tier, because is more material expensive so is wanted that is more powerful.