The Lumia 900 Batman edition, which is already available in the United Kingdom, comes with exclusive The Dark Knight Rises content like themed wallpapers, ringtones and limited edition Batman or Bane character images. The smartphone also comes with 1.4GHz processor, 4.3-inch AMOLED display, 8MP rear camera and 16GB of internal memory.
On the other hand, Nokia Lumia 610 was originally announced at Mobile World Congress. It comes with 3.7-inch display, 5MP camera, 800MHz processor and 8GB of internal storage.
The smartphones currently run on Windows Phone 7.5, but won't be getting the recently announced Windows Phone 8 update. However, Microsoft has stated that it will release a Windows Phone 7.8 update, which will include some features of WP8. The absence of WP8 update is certainly a negative for these smartphones.
There is no word on the pricing right now.