Euphoria - Flephedrone has moderate clear headed euphoria. Plenty of motivation to get work done. Methylone has extreme but short lived euphoria. No motivation to do work on it even at low doses.
Length of activity - Flephedrone lasts slightly longer. Single dose 1-3hrs euphoria + 4 more of residual stimulation.
Sexual performance - Severe dysfunction on both. Impossible to get an erection without a PDE5 inhibitor and then very hard to orgasm. Mixing these with viagra makes my chest hurt enough that it is almost impossible to have sex.
Cardiovascular - For me, flepehdrone seems to increase heart rate and BP more than methylone although both stims are pretty bad in this regard.
Comedown - At average doses flephedrone is mild, methylone is very rough
I found it interesting that my pupils did not dilate on flephedrone unlike on mephedrone. Also, no desire to redose on flephedrone opposed to methylone which is one of the few drugs I have uncontrobaly binged on. I no longer have any desire to use either but if I had to I would chose flephedrone for the cognitive and motivation enhancement.