Surprisingly close to its Japanese counterpart.
http://www.nintendoworldreport.com/news/34440
Feast your eyes on the Western box art for Mario & Luigi: Dream Team.
The West usually gets the short end of the box art stick, just look at Super Mario Bros. 3! Luckily, this time we're getting a nearly identical piece with Mario & Luigi: Dream Team. Lucky us!
Tiny Cartridge noted the only difference between the two. "As expected, the Western artwork doesn’t have that weird Japanese trope with the nose bubble, but they replace it with a weird Western one: the use of “zzz” to represent sleeping noises."
Check out the Japanese box for comparison below.