With the popularity of smart phones and wireless network, location-based services (LBSs) attract extensive attention. The demands on indoor positioning systems (IPS) for the WiFi deployed environments are especially high. In this paper, we categorize the WiFi-based IPSs into two types, namely Received signal strength (RSS)-based and Channel state information (CSI)-based, and compare the practical performances of several WiFi-based IPSs. For the RSS-based methods, we select fingerprinting, trilateration method, sequence-based localization (SBL), and multidimensional scaling (MDS)-based methods for comparison. For the CSI-based method, we choose the time-reversal (TR) algorithm and propose a new experimental scheme to measure its performance. The pros and cons of each algorithm are also discussed.