I really wish people would stop calling FPGA's ASICs. Baikal (so far) has only made FPGA mining rigs. ...
How can you tell the difference?
You probably can't without physically inspecting the chips used.
This is true, and besides that, the fact that Baikals can theoretically be flashed to hash other algorithms gives it away. The Baikal miners being FPGAs also meant that they were less efficient than the D3 X11 ASICS when the D3s first came out. FPGAs are typically weaker than ASICs.