Bk-mdma is the only rc i find even close to on point with mdma.
Mephedrone is nothing at all like mdma like people say. Theres no nystagmus, just euphoria, jaw tension, pupil dialation and It has an amppy body load. Its not 'awful' but its Highly addictive and packs quite a dysphoric mental comedown. It seems to be big amonst the gay communitys, probably due to it providing loads of stimulation.
2ci is a good rc but is now illegal, methoxetamine is good too but both of them arent really like mdma in my experiences with them. Ones a psych and ones a dissociative.
Research 'entactogens' and see what you can find.
Think of it like this, the big boy is mdma, large sert & dopamine release, causeing empathetic euphoria, bk-mdma is an analogue that has very little sert release, lots of dopamine release, so imE feels like mdma with no love.
From what i read mdai is the opposite, high sert release, low dopamine release (thats why its usally combo'd with a dopamine releasing chem to match mdma's effects)
I assume your looking for a substance to party on more than is healthy with mdma?
schedule 1 -research chemicals
Mdma. - bk-mdma, bk-mbdb, mdai, 6-apb (gross imo)
Ketamine. -methoxetamine tileamine
Lsd. - 2ci
Mushrooms. - 2ce
Mdpv. - methamphetamine
Cocaine. -mephedrone
I find some rc's have better comedown some worse, do your research before experiementing as a scientist.
Those are my comparison in opinion from experiences and research =)