No mention of Myriad-Groestl
It is not a matter of opinion. It is a matter of FACT the algos are different.
Groestl-coin doesn't use pure Groestl either.
It uses 512 bit Groestl x 2, then throws away 256 bits.
Myriad uses 512 bit Groestl, then uses SHA256 to get 256 bits. Slightly more secure IMO since there is more entropy in the final result.
Either way, both uses 512 bit Groestl then reduces the result to 256 bits through different means.