Shadow simulacrum and golems use the same minion slot, so one will banish another, if you have active golem and use this spell - golem will be banished and vice versa.
About advantages over the golem... well, there are high level mobs\bosses that have 60+ HD, over 10k hitpoints, BAB over 100+ and something like triple 6d12 damage bonus. So I prefer shadow sim's firepower over golem's safety.
Minotaur is a summon that comes with rare high level drop - a robe of eternal darkness. It has 4k hitpoints, very good hp regeneration and good damage output. But you should be careful with him, if you will summon second one, first will turn hostile and try to kill you, your party, friends and family
. And on EX6 he is quite able to do so...
But it works good with golems and shadow sims.
My builds are not optimized (my first high level arcane build in fact) but it works and you could use it as a basis. I believe there are much better arcane builds around.