Physical Unclonable Functions (PUFs) have gained a lot of research attention in recent years resulting in many different PUF proposals. Several of these proposals were aimed specifically at FPGA implementations. However, often these PUFs are evaluated and implemented for different (and often old) FPGA families with different metrics. Missing implementation details in many papers further hamper a fair analysis, as small details such as the exact routing can have significant impact on the PUF performance. In this paper we aim to overcome these problems by providing a fair comparison of some of the most promising Weak PUFs for FPGAs, the classic Ring Oscillator PUF (RO PUF), the Loop PUF and the TERO PUF. Each PUF is implemented with the same area optimizations and careful manual routing for modern Xilinx Artix-7 FPGAs and several implementation options are discussed. We measure the reliability and uniqueness of the PUF constructs on 100 BASYS-3 boards for a temperature range of -22°C to 44°C and use a glitch-generating core to analyze the vulnerability of the PUF constructs to surrounding logic. Our results show that the RO PUF has the best reliability in the presence of temperature variations while TERO has the best uniqueness of the three considered PUFs. Interestingly, the TERO PUF also shows the highest resistance to surrounding logic. To encourage further research in FPGA PUFs and to enable a fair comparison to future work the implementations as well as the measurement data will be made publicly available.