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Chibi-Tenshi is cuter, but has a slight whiff of "brat" to it. I see something a bit rounder, too. http://www.deviantart.com/morelikethis/305043756?v... (the big pic, not the one in the box)

Chiisana-Tenshi is still cute, but is slightly more elegant and refined.

http://item.rakuten.co.jp/angel-run/angel_run_3mus... MUCH less anime-influenced.

Chibi Tenshi sounds cuter because it's shorter. I love cute things and I give you my stamp of approval! :)