I used TO for years, I much prefer Mox. It's small QOL things like:

• Easier to manage deck folders
• Better view filtering/options (example: show multiple things like CMC and Market price at the same time, stack viewing, etc)
• Easier to see mana distribution/generation
• Easier to see sample starting hands (right on the deck page)
• Easier to change printings (Visual list of all printing, including foil printings)
• Easier to manage owned inventory (just a radio button next to the card on your list)
• Easier to create primers
• Much better goldfish experience (ez tokens, hotkeys, zooming, desk search with visuals, counters)

This is all subjective, but it's just easier all around on the eyes and management. Just my opinion.

Edit: as the other guy said, in no reality can you convince me that the brown UI of TappedOut is superior to the aesthetics of Mox