I will do this with full movepool and best 4 move coverage, separately. I will be excluding Hidden Power for the sake of "breaking" the comparison. Also, keep in mind the type coverage checker I am using counts different forms of a Pokémon as a different Pokémon. :P
Full Movepool:
Simisage- Normal, Ghost, Grass, Fairy, Fighting, Poison, Steel, Dark, Flying, Ground, and Rock (11 types)
Type Coverage: 42 Neutral, 882 Super Effective.
Simipour- Normal, Ghost, Water, Fighting, Fairy, Poison, Ice, Steel, Dark, Rock, Flying, and Grass (12 types)
Type Coverage: 77 Neutral, 847 Super Effective.
Simisear- Normal, Ghost, Fire, Poison, Fairy, Fighting, Steel, Dark, Grass, Rock, and Flying (11 Types)
Type Coverage: 68 Neutral, 856 Super Effective.
Best Moveset coverage:
Simisage- Fighting, Rock, Grass, Flying
Type Coverage: 4 Not Very Effective, 225 Neutral, 695 Super Effective.
Simipour- Flying, Rock, Ghost, Fighting
Type Coverage: 243 Neutral, 681 Super Effective.
Simisear- Flying, Rock, Ghost, Fighting
Type Coverage: 243 Neutral, 681 Super Effective.
Overall, Simisage has better coverage in both categories. :P
Type Coverage Checker
Hope I helped!