the fk1 is still reliable, it's not exactly old.
Honestly any new mouse with an optical sensor is reliable.
I'd recommend checking out this youtube channel: https://www.youtube.com/channel/UCGJaDZC7PChgd-XMwcbZkiw
My personal best are probably the logitech g1 pro that was just released, basically has the g100 shape but g303 sensor, the Nixeus Rivel and the DM1 pro.
But yeah I'm currently using the fk1 and it has no problems