Are you talking about OpenBazaar? If so, i think it's not that similar since OpenBazzar was more decentralized, which also makes it's less practical to use.
Yes, there was OpenBazaar, maybe that project still exist, I saw it restart several times.
One big advantage for monero is privacy, and I have seen in many services that people use monero more than bitcoin for payments.
I have already made several purchases on XMRbazaar and each time it was very good.
Nice to hear someone who actually used this service.
You don't have to answer if you don't want, but I am interested if you purchased physical or virtual items?
International shipping can be a mess even with fiat payments and big established platforms.
What I like is that most sellers have their SimpleX invitation associated with their profile, so you can check all the details and chat with them before buying.
That is another positive thing for sure.