I have tried both Fels Naptha and Zote and one called Fan (have to buy at Asian grocery store but it's the best). Here are the differences I have found. Other people may have had different experiences.
- Fels Naptha has a lower water content, so if you are grating it to use it in home-made laundry detergent, this is the easier to grate than Zote.
- I have only tried the white Zote, but the water content is much higher so it is difficult to grate using the fine side of the grater (it's like trying to finely grate mozarella cheese).
- both smell clean, not perfumy, but the Zote seemed to have a stronger scent. If you turn it into laundry soap you wont notice it, but if you are using it for spot cleaning and are very sensitive to smells, you should sniff the package before buying
- in cold water it seems like Fels Naptha disolves quicker (when both were turned into powder laundry detergent)
- I soaked a very smelly sports bra in Zote and while it did a great job of cleaning it and removing the nasty smell, it did seem to leach the color out of the sports bra way more than Fels Naptha. I used the white Zote, which the package describes as "brightening". We only use the Zote laundry soap when cleaning whites, towels, sheets and that kind of thing. I don't really use it on my dark work clothes
- Around us we can Zote for $1 for a large bar and the Fels Naptha is $1.29 for a smaller bar.
- Fels Naptha is made in the US. Zote and Fan are not.
I hope that helps. I am using up the Zote we bought (DH bought tons of both because it can be hard to find), but will go back to Fels Naptha only.