That's putting it in some bullshit terms. That's like if I said, Mate, there is a big difference between someone who uses amphetamine now & again and an E-tard who drops MDMA every weekend
That isn't true. There are people in rehab for it, especially in conjunction with abusing other drugs – what rehab people call “cross addicted”. But that shit is all psychological, so you know ¯\_(ツ)_/¯ To me that boils down to compulsive behavior pattern disorder. Physical dependency is a different matter. Say what you want, but the come down from MDMA sucks shit compared to… well no, actually, coming down from either kinda sucks unless you have a benzo and enough time to sleep…
MDMA works mainly on Serotonin (5-HT), as you pointed out; however, it also affects dopamine and adrenaline, just to a much lesser extent. Furthermore, the psychedelic amphetamines are primarily serotonergic with all of them exhibiting a strong effect on 5-HT2A. So it's inaccurate to say “amphetamines work mainly on dopamine”; some do and some don't. It really just depends on the compound in question… I'm talking about DOM, DOB, DOI, DOC, etc., btw, regarding psychedelic amphetamines. There are entries for each found in PiHKAL by Dr. Alexander Shulgin.
Says who? Let's say I had to be in a car with someone else driving and had to choose between that person being high on MDMA or high on speed (Idk why I would be in that predicament, but humour me for a moment, s'il vous plaît), I would opt for the latter simply because speed is less inebriating than MDMA. If you're talking about the primary amine, amphetamine, you're not crossing into neurotoxic range if you dose sensibly, unlike MDMA which is neurotoxic every single time it's used on account of MAOs converting serotonin into alpha-methyldopamine when it floods into dopamine receptor synapses. (To be fair, I mostly consider this kind of damage to be negligible so long as you don't overdo it with frequency and chasing an MDMA high; after all, drinking booze is also neurotoxic every time…)