What are the alternatives?
You can get a faster and bigger storage device. That seems unrealistic in this case.
You can use a traditional file system (like UFS or FAT). Would that have significant advantages? I doubt it, although it is possible. Here's why. ZFS has many interesting features, like being an appending or log based file system (it tends to not overwrite things in place), and implementing CRCs on the data, which are stored in on-disk metadata (its ability to implement RAID within the file system layer is not relevant here, since the OP has only one device). These are all really good things, but they also imply that the IO pattern of ZFS is different from traditional file systems. When I say "IO pattern" I mean IO sizes, sequentiality, random seeks, direction and size of seeks. That different IO pattern might work better on eMMC, or it might work worse. I don't know enough about the FTL (flash translation layer) that's used on eMMC chips to make any prediction here.
My suggestion: Try ZFS, and see what happens. If the performance is appropriate for your use (for your workload), then just go with it. ZFS is nearly universally a better file system. If the performance is not good enough, then try a traditional file system, and check whether it gives you better or worse performance.