I think I'd take Marmite over M1. It's better than being at baseline but what it does do doesn't seem to be worth the strain it puts on my heart, I find the peripheral stimulation from M1 lasts longer than mephedrone (elevated heart rate mainly), but don't take that as me saying M1 is more toxic, just that it lasts longer. Meph is the only thing my feet have swollen on, so I know it's a devil in it's own right, but I'd rather spend an evening with the devil (mephedrone, I'm trying to do a metaphor, keep up) than spend it bored with my grandma(M1), despite her being as lovely as she is. No idea who I would personify MDPV as (GF?) but it has caused the worst skin discolouration, no swollen feet or anything but very cole hands and the back of my arms turned dark purple. This was actually in combination with M1 now that I think about it; I'd run out of meph the week before.
tl;dr meph is worse for me, but gives better reward. M1 gives a modicum of reward, but it's so paltry that it's not worth the elevated heart level for what really does seem a long time, it continues at least 3 hours after ingestion and i feel I'm being extremely conservative with that number because I think it can last as long as 6 to 8 hours (the heart beat).
EDIT: M1 doesn't keep me awake like mephedrone does, I think I could bomb half a gram of M1 and be asleep in 3 hours, it's just you don't really want to sleep and trying to sleep just makes my heart beat fill my senses, because it's dark and quiet, etc, etc I can feel and hear my heart but not much else. I have still gotten to sleep though, it's the mephedrone and MDPV that keeps me up. My friend was kept up by an M1 bomb I eyeballed, which, looking back now I've been using scales must have been well over 500mg, maybe as much as 700mg. I had the bigger bomb of the too as well, but managed to sleep from 6 to 8, amazing what a difference 2 hours sleep can make. Went into his room and he was still awake buzzing his tits off, pupils as big as they'd ever been the previous night and I was back at base. Must be my hardcore meph abuse allowing me to shrug the lesser stimulants off.