Comparative studies assessing outcomes with the three device-assisted therapies could help to individualise treatment for patients living with Parkinson’s disease. We designed a single-centre non-randomised prospective observational study assessing the quality of life (QoL), motor and non-motor outcomes at 6 and 12-months in patients treated with subcutaneous apomorphine continuous 16-hours infusion (APO), levodopa-carbidopa intestinal gel (LCIG) or subthalamic nucleus deep brain stimulation (STN-DBS). In this study, 66 patients were included (13 APO; 19 LCIG; 34 STN-DBS). At baseline, cognitive, non-motor and motor scores were significantly less severe in the STN-DBS group, whereas the LCIG group had a longer disease duration and higher non-motor scores. In the APO group, there were no statistically significant changes in non-motor, motor and QoL scales. The LCIG group had significant changes in QoL and motor scales that were significant after multiple comparison analysis at 6 and 12-months. The STN-DBS group showed improvement in QoL scores and non-motor and motor scores at 6 and 12-months after multiple comparison analysis. In this real-life prospective study, device-assisted therapies showed differences in their effects on QoL and motor and non-motor function at 12-months. However, there were also differences in baseline characteristics of the patient groups that were not based on pre-determined selection criteria. Differences in characteristics of patients offered and/or treatment with different device-assisted therapies may reflect within-centre biases that may, in turn, influence perceptions of treatment efficacy or outcomes. Treatment centres should be aware of this potential confounder when assessing and offering device-assisted treatment options to their patients and potential baseline differences need to be taken into consideration when comparing the results of non-randomised studies.