One of the main selling points for ZFS is the end-to-end cryptographic verification of file contents as well as all metadata. Everything in ZFS is hashed, and verified during reads. Without ECC RAM, your hashes are vulnerable to corruption due to bits being erroneously flipped in RAM. If this happens with non-ECC RAM, you're never going to know, and it will cause corruption. With ECC RAM, these events are not only detectable, but also fixable.
Regarding ZFS "requiring a huge amount of RAM". Most of this comes into play if you have dedup turned on. Then you really need a lot of RAM. Without dedup enabled, and if you're OK with mediocre performance, you can get by just fine with a "normal" amount of RAM. It's well-known that filesystem performance increases with more RAM - this is not something that is unique to ZFS.