The Proxmark3 Dev Kit 4 (RDV4) from RRG/ProxGrind is more compact/portable and brings various improvements to the open source design. Its antennas are highly customizable and there is a new multifunction multiplexing interface to support additional components such as an external battery, external active high powered antenna, bluetooth interfaces, and more.
Whether you’re in the field, in the lab, or in the classroom, the Proxmark3 is the RFID tool of the trade when it comes to sniffing, reading, and cloning RF Tags. Proxmark3 can run independently from any computer (powered by an optional battery) and offers advanced functions like offline encryption, online sniffing, default key cracking, data dumping, or the ability to run simulations.
It is currently the gold standard tool in the security world when it comes to RFID research.
If you are serious about RFID and you dont have this tool, then you must not be serious. This tool pricey, but you will get your moneys worth once you FLASH it and start using it. I used my raspberry pi and followed the github instructions which are simple and easy. What are you waiting for?