Uši (Pro) have higher sensitivity, lower self-noise but bigger size. MikroUši (Pro) are tiny and have better frequency response. basicUcho has the same (or slightly higher) sensitivity than Uši Pro, but lower max SPL (110 dB SPL vs 122 dB SPL).
For very quiet sources such as natural sounds we recommend using Uši Pro or basicUcho. They also offer more accessories. mikroUši come handy when you need discreet recording solution and don't mind the slightly higher noise-floor.
Check a full comparison table here.