I am slightly confused as I have the budget for either but given that the 550D is newer model whereas 50D is better in the sense that it belongs to a higher series. Are there any other deciding factors that I missed? I am buying because I love photography and I won't be using it just casually.
I own both, and while both are good cameras, to me the differences come down to whether you want to use a camera that is keeping with the form and functionality of Canon's 'professional' series of cameras, or you don't care about that.
- Feels more solid (more metal vs. plastic)
- Screen on top
- 2 adjustment wheels (550D only has 1)
- PC connector for a flash
- AF points are generally more responsive
- Brighter viewfinder (uses a pentaprisim instead of a pentamirror like the 550d)
- Higher burst rate (6.3fps vs. 3.65fps)
- Wider LCD screen
- More megapixels (18 vs. 15.1)
- More advanced metering system (iFCL)
- 1080p video
Generally speaking the advice that I'd give is this: if you need to shoot video, or you really need the 3 megapixel jump up to 18mp, then go with the 550D... Otherwise, all things being equal, the fit, finish features and layout of the 50D are more in keeping with what is available on the higher-end Canon bodies As a 'non-casual' photographer over time you're more likely to migrate up to a body higher in the Canon food-chain, instead of down to a more consumer-oriented one, and with the 50D you'll already be used to the layout and operation of all the knobs and features of the 'pro' line of cameras (for the most part).
It seems that as Canon does not release all their camera models at the same time, inevitably models at any point in time seem to have close or similar specs where you would not expect them, such as with the 550D and 50D. The 550D is significantly newer than the 50D.
In any case, ignoring the technical specs, the largest difference is in the handling and the flexibility of the systems. The 50D is physically a bit larger, and usually described as much more comfortable in the hand. There are many, many more custom functions, allowing for significant customization of buttons, features and camera operations.
One particular feature I prefer is the ability to separately adjust shutterspeed with the front control wheel while the back one will adjust aperture. This allows for simple and fast adjustments making Manual mode actually useful and productive.
Also, support for micro adjustments of lenses is another critical difference found in the 50D.
That being said, the 7D is light years above even the 50D!
If you don't care about video - undoubtedly go for the 50D. Once I moved from the Rebel XT (350D) to the 7D, I could not look back! The difference in the handling of the two bodies is really great. Not only the bigger body is much more convenient (at least for my hands) but the extra controls really make a difference. The higher resolution is BS b/c you will most probably be limited by your lens resolution.
Now, it seems like you can find some good deals on the 60D nowadays. It might worth the extra money for you so check it out.
Last - I assume it is your first DSLR. If so, just consider the Nikon offerings before committing to Canon. That said, I love my Canons and think it is a good investment in the long term.
I vote for the 50d. The screen on top, plus quick access buttons ontop, plus the two dials and joystick provide /a lot more/ in terms of usability than the 550d.
In fact, the 50d has more usability features than the 60d! and the 6d for the matter.
In terms of video, if you can live with silent movies then you can get Magic Lantern for the 50d and get silent movies.
They have the pretty same sensor, it's just that 550D has more megapixels which I think you don't need, but the 50D is semi-professional which means you have full control of the camera and it lets you do whatever you want for real, not just some automatic functions, plus the 50D has better build quality, it's heavier with magnesium alloy construction etc.
- 50D has faster continuous shooting up to 6.3frames per sec.
- And faster shutter speed up to 1/8000s
- And if you don't care about video recording you can go for 50D.
In reality you can't compare a semi-pro model with entry level products.
I already have a Canon EOS 50D and i think it's pretty good camera for it's money and what it can do, but first check the camera feel the camera before buying it.
Nikon has many good models but they are pretty expensive if you want to go to the good ones.