The book Magics of Golem Enhancements describes the powers the Shield Guardian gets from each of the nine spells pretty well. In particular, according to the guardian's OnSpawn script:
- Greater Spell Mantle -> Spell Resistance 32 (superseding the default 26 SR)
- Bigby's Crushing Hand -> Strength Bonus +4
- Greater Sanctuary -> Deflection AC Bonus +4
- Time Stop -> Regeneration +8 (in addition to the +5 regen the golem already has)
- Premonition -> DR 30/+5 (superseding the default 20/+3 DR)
- Mass Haste -> (permanent) Haste
- True Seeing -> (permanent) True Seeing
- Chain Lightning -> casts Chain Lightning (at caster level 3) when Shield Guardian is hit
- Mordenkainen's Disjunction -> casts Greater Dispelling (effectively at level 15) when Shield Guardian hits
(Note also that the Shield Guardian has a robe equipped, so his AC can potentially enhanced with the Magic Vestments spell.)