i think lei's are not the easiest to keep alive. they need large space setups and usually commit suicide thus are harder to keep til old age. how many do you know of that are huge in the hobby?
silvers are the easiest to keep alive, super hardy and grow the fastest.
blacks are like silvers, but grow slower. same concept on blacks, easy to keep alive (keep ur lids covered properly) and super hardy.
i have both silvers and a lei, my lei grew close to 1.5" per month in length, and body mass jus keeps fattening by the day.
silvers jump to 22" super quick in life, then slow down a lot and fatten up as they grow in a slower growing process.
jardini's are super super easy to keep. jus like a lei but not as likely to be so jumpy, but meaner temperment of course which means tankmates are not likely but is possible