iFlicks is more than just tagging though, right? It's ripping, encoding, and tagging? I've been very happy with Handbrake, so why would I make the switch? Is the quality better? Are the file sizes smaller? Is it faster? All steps in one program? Why choose iFlicks over Handbrake/Subler?
Don't, use both like I do.
I use Handbrake for all my encodes, top of its game if you ask me and way faster at encoding than iFlicks.
But, iFlicks is insane at tagging. Once you encode the file in Handbrake, you can set it in Preferences to open it in iFlicks (or drag the file manually) it will gather all the meta data automatically, quickly and amazingly and present it stunningly. Then if you select "Flatten to quicktime file" it just adds the meta data to the encoded file and adds it to iTunes, takes like a minute to do. It doesn't re-encode it or anything, just adds on the data.
It does everything Subler does. HD tags, rating, etc. Lots of nice preferences too, I have it set to delete the original file and add it automatically to iTunes.
AND, if you already have files in iTunes, it can install an iTunes script to work right within iTunes for tagging.
So yeah, Handbrake is the best for encoding, iFlicks is the best for tagging. Great combo.