Right now I'd choose Lemmy. Summit on mobile and photon on desktop.
Piefed is a close second, but still has a ways to go. Honestly, I could see it surpassing Lemmy soon.
I haven't driven Mbin too much, but it's pretty neat conceptually. I wouldn't count it out if you want to be able to microblog from the same platform. Kind of novel, but I found the experience to be disconjointed overall.
Not enough to convince them though, right?