I have not seen the Joaquin Phoenix as the Joker yet, but based on the previews; I would say Jared Leto is my favorite. I enjoyed how he put a modern twist on the character of the Joker.
I related to his appearance with the tattoos and the personality of hip hop music. I think it fit the times, but as a classic movie fan, I can understand why someone prefers how Joaquin Phoenix portrayed the character. It takes it back to the original Joker from the silent film and comic books. From the previews, his portrayal looks scarier that Leto's, and it looks like he really dug deep for his portrayal.
Even though some people think that Jared Leto did an excellent job as the joker, it is very exciting to see Joaquin Phoenix take over the role. Phoenix is set to refresh the DC Villain and help to bring the franchise out of its fragile state.
Phoenix is infamous for being a brilliant method actor, while Jared Leto's version is more predictable and juvenile. Also, Phoenix's talent is on par with Heath Leger's. Phoenix is also a master at playing creepy. He can be very dark and intense at times, which is perfect for the gritty character study that DC is hoping to portray.