fragilesi said:- With the 550d I certainly landed on my feet, for its price point it has always felt a hell of a camera.
- It’s prudent to wait a bit longer (70d price drops, 7d MkII news possibly), I’m just about to hit 100k actuations on the 550d, I’m not sure how long these things last but at my level there’s still a lot it can help me learn, I'm sure of that much.
True, it is. And also, True, it is.
Your 550D might be nearing it's tested shutter durability, some keep going much longer, some fail much sooner.
You have a working camera for now it seems so no real need to panic buy.
I haven't suggested full frame because it isn't the answer to your question, or by any stretch, your dilemma. Some folk just like saying full frame full frame a lot I guess.
The 7D and 70D AF is similar in phase mode, but in terms of flexibility and tweaking etc the 7D has more user variables, if you are very serious about AF and want the best possible within budget the 7D still has the upper hand.
Just. The 70D will probably work just fine out the box, the 7D needs a bit of playing about to get sorted, but it will reward you.
However, keeping shooting with your 550D is fine too.
I would recommend the following, if you don't already..
1. Select the centre AF point only. It's the only cross type.
2. Set the drive rate to burst. Get a class 10 SD card.
3. Select AiServo for sports and nature. Track track shoot. Track track shoot. This really helps predictive AiServo. And will help keep things in focus when your mirror is flapping around during a burst. The small short bursts help you keep things composed and also let the cameras buffer clear, ready for the next important bit. If you keep your finger on the shutter everything will slow to a crawl.
4. Consider faster aperture lenses. They will also really really help your AF, especially on your current body, but every EOS DSLR has improved AF with f2.8 or faster lenses. Something like a 200mm f2.8L is a very fast focusing high quality lens that will also work on full frame if you go that way. Certainly a brilliant sports lens, if not really long enough for a lot of nature.
5. Consider a mono or tripod. Especially where any panning is involved. Mono-pods cheap and have virtually no footprint. If you pan, you'll pan 10x with a little support. And this will also really help your AF keep up.
6. Finally, consider JPEGS in good light. This will also speed things up and clear your buffer giving you more burst depth.