we are talking about altcoins not bitcoins . anyway i think there is no best altcoins because all of them do have a certain disadvantage . some alts do also have an advantage that cant be found on the other. 

however when if you say semi best altcoin , i  think etherium is probably the one because etherium is the only first altcoin that exist after the creation of bitcoin.  etherium do also have a lot of usage when compared to other altcoins .