Voyager is definitely the most polished and great for those who used Apollo for Reddit. It is also very actively developed. For the Android users who do not mind the iOS aesthetic, Voyager is one of the few Lemmy clients on F-Droid.
Thunder is also a great option. I personally prefer its UX more than Voyager, but it is not quite as polished.
I loved Apollo and appreciate Voyager but it doesn’t respect hiding read posts very well so I turned to Mlem which is now my favorite. The v2 beta is even better, adding easy markdown formatting and some nicer UI enhancements (the vote counter scrolling up or down on vote is a nice touch).