I definitely prefer Emmanuel. That spelling I would argue also has more overt religious connotations - to me, anyway. Immanuel just makes me think of Immanuel Kant.
Please rate my personal short name lists (the latter includes combos):
www.behindthename.com/pnl/69381www.behindthename.com/pnl/69381/91835 (updated)
http://greens-end.myminicity.com