Any time someone asks what the "best" is, I get that bad feeling deep down...

There is no best. No best camera, no best editor, no best car, no best anything. There are simply choices. Thus you will find no thread that tells you what the best intermediate is.

Cineform is "the best" codec if you need a 10bit codec that creates the smallest files, and holds up to multi-generational encodes. It has a number of pitfalls, the biggest being that costs money for anyone who wishes to write in that codec. Cross platform use can also be a bit tricky.

DNxHD is free, excellent, can be 8bit or 10bit, travels cross platform nicely. However, it creates .MOV files from the free version and that doesn't always work for people's purposes. Especially on the PC.

MXF is not a codec. it's a container. On these forums, MXF usually is implying the Sony Mpeg2 codec inside MXF. It's fast, decodes easily, but doesn't travel well to other NLEs, on PC or Mac, and requires rather good bitrates to maintain quality. It's also lossy compared to common uses DNxHD or Cineform, and will not hold up to multi-generational rendering. It's also long-GOP which can cause timeline performance issues when applying effects, or doing things like reverses.

The Matrox VfW codecs are also Mpeg2 based but are not long-GOP. So they offer excellent speed, and are timeline friendly. However, they require significant bandwidth to maintain quality, thus giving rather large file sizes. They also store in a .AVI container and don't travel well cross-platform, and in some cases don't travel well to other NLEs on the same platform..

These are called intermediates because they are an intermediate step between the acquisition codec and the final delivery codec. Most people these days are delivering with Mpeg2 for DVD, Mpeg4/VC1 for BluRay, or Mpeg4/WMV for the web.

Thanks a lot musicvid and Perrone, you did help a lot to clear things up for me.
I guess "best" was not an elegant adjective to specify what kind of answer I was looking for, but your answers made things easier anyway.
I basically asked because I still find my Canon rebelAVCHD files to be somewhat heavy in V10, even though I´m on a quad core mac pro with bootcamp / win7x64. I´m still in the learning process as far as NLE and the lot of new problems and questions it generates are concerned...

"I basically asked because I still find my Canon rebelAVCHD files to be somewhat heavy in V10, "

Despite all the disclaimers we gave, some here will suggest that Cineform is "best" for these files based on experience. That is, assuming they will remain in a PC environment, not ported over to FCP.

Another thing you can do is shoot in 720p natively, which will smooth things out considerably.

1080p transcoded to an intermediary format is going to give you a higher quality finished product than working with 720p native format.

I really don't know shit about this either, but I was having problems editing my .mts files in Vegas and I downloaded and bought Neoscene and since then I'm a very happy man. My files play back perfectly smooth, even in reverse! Something the .mts files couldn't do at all. Before I couldn't cut to music, now I can. If you're editing video of your afternoon at the park you might not care, but if you need accuracy you'll love it! IT does take some extra time, but I just start the process and leave for a few hours. But it's well worth. If you download Neoscene, make sure you get the extra codec for the audio, I"m not sure where I found it, but someone posted into one of my posts recently, it shouldn't be too hard to find, without it you'll get .avi files with no audio.

. Let us know how you find it.