Background and aims: The introduction of Advanced Hybrid Closed-Loop system (AHCL) has profoundly changed type 1 diabetes therapy. This study primarily aimed to assess the impact on Glycemia Risk Index (GRI) and other continuous glucose monitoring (CGM) metrics when switching from one of four insulin strategies to AHCL in type 1 adult patients. Methods: A single-center, retrospective pre/post observational study; 198 patients (age 44.4±12.7 years, 115 females/83 males, diabetes duration 24.7±11.6 years, HbA1c 7.5±0.9%), treated with different insulin therapies (MDI, CSII, SAP with PLGS, HCL) were assessed before and after switching to an AHCL (MiniMed 780G, Diabeloop Roche, Tandem Control-IQ) at 1, 3, 6, and 12 months. Mixed-effects multivariable regression models were used to estimate the mean pre/post variations at different time points, adjusted for potential confounders. Results: A month after the switch, there was a significant improvement in CGM metrics and HbA1c for all patients: GRI -10.7, GMI -0.27%, CV -2.1%, TAR>250 -3.7%, TAR180-250 -5.6%, TIR +9.7%, HbA1c -0.54% (all p<0.001). This improvement was maintained throughout the observational period (at 3, 6, and 12 months, with all p-values <0.001). When improvements across the 780, Diabeloop, and Tandem CIQ devices were compared: the Diabeloop demonstrated significantly better performance in terms of GRI, GMI, CV, TAR>250 at T1 (for all p<0.01); the 780 recorded the highest average decrease in TAR180-250 (p=0.020), while Tandem achieved the most significant reduction in TBR54-69 (p=0.004). Conclusions: Adopting an AHCL leads to a rapid and sustained improvement in GRI and other parameters of metabolic control for up to a year, regardless of prior insulin therapies, baseline conditions or brands.