Fitch is hypoallergenic. I think Kaytee C&C is as well. Not sure about Carefresh as there has been the odd case of someone thinking a hamster was allergic to Carefresh.
I am still a Fitch fan
Of the Kaytee C&C I prefer the white. The texture of the coloured ones is slightly different. The "natural" brown one is ok but a slightly different texture. The red coloured one I found had an ink smell but it wore off when aired out for a while.
You need to be careful though as some colours of Kaytee C&C are also scented so always avoided any scented bedding as that is bad for hamsters.
Kaytee C&C didn't used to be available in the Uk - that is quite recent. I think it changed as well because it used to be like strips and now it is more small pieces of paper a bit like Fitch.
Both are absolutely fine. But when filling a 100 cm cage from empty I can easily use a third of a 10kg bag of Fitch. So it works out a lot cheaper. And after that the rest of the bag lasts ages with spot cleaning mostly.