This paper presents a comparative analysis of two advanced positioning services, commercial Precise Point Positioning-Real-Time Kinematic (PPP-RTK) and Network RTK (NRTK), for vehicle-borne kinematic positioning in urban and suburban environments in Central Italy. The study focuses on evaluating the performance of low-cost Global Navigation Satellite System (GNSS) receivers in real-world conditions, aiming to assess their suitability for high-precision applications. This research is motivated by the increasing demand for accurate and reliable positioning in mass-market applications, such as Cooperative Intelligent Transport Systems (C-ITS) and location-based services (LBS). Although low-cost GNSS receivers are widely available and cost-effective, they often struggle to meet stringent accuracy requirements, particularly in environments affected by multipath, obstructions, or GNSS-denied conditions. To address this challenge, the study investigates the potential of the PPP-RTK technique, which integrates undifferenced atmospheric corrections, precise satellite clock corrections, and additional sensor data, including an Inertial Measurement Unit (IMU), to enhance positioning robustness. The experimental setup involved a field test with three navigation devices equipped with u-blox low-cost GNSS receivers, augmented with either a commercial PPP-RTK service or the regional NRTK service from the Umbria region. The test trajectory was designed to cover a diverse range of real-world scenarios, including areas with limited satellite visibility, high multipath interference, and signal obstructions such as tunnels, overpasses, and tree-lined roads. A particular focus of the analysis was given to the altimetric component of the positioning solution. Height estimates from the different positioning techniques were compared both with the height positions of two geodetic receivers and with a Digital Elevation Model (DEM) to assess accuracy and reliability, enabling a detailed evaluation of vertical precision in challenging environments. The results indicate that all three low-cost GNSS receivers achieved decimetre-level positioning accuracy. PPP-RTK/IMU integration and NRTK performed similarly, while standalone PPP-RTK exhibited slightly worse performance in complex scenarios. The IMU integration appeared to stabilize vertical positioning and enhance overall reliability, while supporting continuous updates in GNSS-denied environments. These findings highlight the potential of low-cost GNSS receivers when combined with advanced correction services and sensor fusion techniques, offering a viable solution for high-precision positioning in cost-sensitive applications.