How big is the tank going to be?
Cardinal shrimp need hard, alkaline water with higher temperatures to thrive, and if you want them to breed you cant keep them with small fish. So, while beautiful, you cant keep them with much other than snails.
If you really like the idea of breeding them though, they would be good for a small 15l-ish tank.
I like CRS myself, but thats because you can keep them with so many other things safely (well, it was safe before I added my baby bettas
) and have a big variety of inverts.
The inverts I have in my 30" tank are CRS, big armoured filter shrimp, micro crabs, cherry shrimp, Malaysian rainbow shrimp, purple zebra shrimp, bumblebee nerites, tiger nerites, different coloured apple snails, then trumpet snails, ramshorns, pond snials and tadpole snails.
They all coexist peacefully and don't interbreed. Though the cherry shrimp certainly seem to crowd out the CRS so I wouldn't recommend keeping them together if you want to keep CRS. I just like seeing all the life bustling and breeding, but with more variety.
Shrimp I've always wanted to keep and breed would be snowball shrimp (their eggs are so cute lol), they are easier than CRS and Sulawesi shrimp, basically like cherry shrimp.
There's also tiger shrimp and the various other forms of
Caridina cf.
cantonensis, but IMO none available in the UK compare to CRS
.