Everyone should use whatever their heart desires, and for me the voyager app is beyond perfect (Android, PWA.) I havent used Sync so it might be better in some aspects but I am content with voyager.
P.S. If you really like a client you should donate any amount to the developer(s) to help them keep their app awesome!
Out of the Lemmy apps I tried out, Voyager is the app I used the most, and it is definitely a great app! But I did miss the smoothness and customisability of Sync, so I will most likely use that on my phone from now on.
As much as I like Voyager, I do feel like there is some slowdowns/stuttering and feeling of the GUI not always doing what I intended to do. Not a lot, but enough to sit in the back of my mind.
That being said I'm still using Voyager on the iPad and also in the browser on my PC! (Which reminds me that I should try installing the Voyager app from the iPad app store, maybe that'll actually fix the occassional slowdowns.)