Canon has released the 550D as an upgrade to 500D. It has inherited some of the features of their high end 7D while offering a cheaper alternative to 7D.
Key features:
- 18 Megapixel! Will this megapixel race ever end?
- ISO 100-6400 (Expansion to 12800) , similar to 500D
- 1920X1080 Full HD Movie Recording
- SDHX compatible
- External microphone support 3.5mm stereo jack
- Weight 530g
Limitations:
- Fixed LCD
- No in camera RAW conversion
Canon 7D Advantage over 550D
- Faster burst speed 8fps vs 3.5fps (550D)
- Weather proof sealing
- Top LCD
If faster burst speed or weather proofing is not your requirements, 550D would work out better for you.

i jst wanna know if…..Canon EOS 550D in rebel T2i r d same modls….if dey r thn y 2 names???
r cannon EOS 550d n t2i d same….
canon EOS T2i (USA), Kiss X4 (Japan), and 550D (elsewhere) are different names of the exact same camera.
see http://www.dpreview.com/reviews/canoneos550d/page2.asp