Here's a list of ''summoning-themed'' spells a wizard has. (not to say that the druid isnt a good summoner, its my favorite class, but I think the wizard makes for a better summoner).
Dancing Lights
Unseen servant
Floating Disk
Find Familiar
Flock of Familiars
Earthen Grasp
Galder's Tower
Animate Death
Tiny Hut
Summon Lesser Demon
Arcane Eye
Magic Circle
Instant Summon
Conjure Minor Elemental
Black Tentacles
Galder's Speedy Courier
Secret Chest
Faithful Hound
Private Sanctum
Summon Greater Demon
Conjure Elemental
Infernal Calling
Planar Binding
Create Undead
Create Homonculus
Magnificent Mansion
Mordenkainen's Sword
Clone
Simulacrum
Wish
Mighty Fortress
Considering the concentration limit, and since the druid's list is like 90% concentration spells, I think Wizard have a easier time playing ''pet master''. The Conjurer just add a little more stuff to an already quite powerful summoner.