Entry level dSLR's, for the most part, are using less expensive SD and SDHC memory cards,
So, why do pro-sumer and professional cameras (for the most part) use only Compact Flash (CF) memory? Is it a performance, reliability or durability issue?
Initially the reason was performance and capacity. A lot of the pro-level cameras went CF because you needed the performance and, usually because a pro shoots RAW, the capacity which the original SD couldn't match. Not to mention there was a point in time where SD was more expensive as a result of volume sales differences. SD is now cheaper thanks in a big way to the proliferation of small devices that used them such as point and shoot cameras, media players, etc.
Anyways, the speed/capacity issues largely evaporated with SDHC and will evaporate with SDXC. Then I think you will see a big move, in fact the shift is already happening without SDXC support in any camera. Canon's 1Ds as noted, but even Pentax stayed SDHC with the 645D medium format and that is miles away from a consumer camera. Also what we are starting to see is dual card support because SD cards are nice and small, that's a nice thing to have and impractical with CF.
Mostly because CF has faster read/write speed than SD card. SDHC has a higher capacity (more space) but not necessarily faster read/write speed.
Some high-end CFs allow parallel read/write (the interface allow this), but not SD/SDHC. So some high-end camera usually take advantage of this in combination with their buffer.
Now Rob Galbraith did lots of test ... and his conclusion is basically it does not really matter for most of us - unless you have that Nikon D3s and do a lot of rapid continuous shooting.
And since this thread has now been resurrected, I'd like to add another reason that I'm surprised nobody has mentioned.
When you're shooting day in and day out to earn a living these things really matter!
I guess in part because CF cards are bigger, and so it's easier to develop faster and larger quantities of memory in large-sizes, before scaling down to the smaller SD cards later on. I think the added bulk and resilience of the more substantial CF cards.
I'd imagine most of the professional camera body users also have a fair amount already invested in CF cards, and so are likely to be reluctant to have to replace all of their CF cards with SDs.
Some professional DSLRs do support SDHC, such as Canon's 1Ds Mark III. Historically, Compact Flash offered higher capacity with miniature hard disks, although with advances in flash memory, solid state media has long overtaken it. Manufacturers don't want to give any excuse for photographers from upgrading, so tend to carry on supporting CF.
As SD cards are getting faster and more common, they should gradually displace CF cards in the professional market.
The fastest commonly-available SD cards on the market can reach speeds of up to 100 MB/s, so performance is much less of an issue than it once was. With the introduction of UHS-II (and with Toshiba already having developed a 260 MB/s card), it's only a matter of time before more pro-level cameras adopt SD cards.
Most laptop computers now have a media reader that accepts SD cards, but CF cards usually require separate equipment to read. The vast majority of consumer cameras accept SD cards, so it's a lot more convenient for enthusiasts to be able to keep using their existing memory cards when they move up to a more powerful camera.
The real reason CF is still on the market is historical: CF was once widely used for both professional and consumer cameras. When SD cards were first introduced (as MMC), they were significantly smaller than CF cards making them ideal for compact cameras, but had technical limitations which significantly limited their speed and maximum capacity. CF cards communicate using the PATA (or EIDE) interface once widely used by hard drives and are physically much larger than SD cards, making it easier to design for high performance and capacity. They were therefore retained for use in professional cameras where compactness is not as important as speed and capacity. Now that the original technical limitations of the SD card interface have been overcome, SD cards should gradually replace CF cards in pro-level equipment.
This transition to SD in high-end equipment is already in progress. Enthusiast-class cameras like the Nikon D600 and D7100, Canon EOS 6D and 70D, and Pentax K-3 all take SD cards and have UHS-I support. Given that cameras in this class have traditionally used CF cards, we can expect this transition to continue into the semi-pro and professional classes.
It really isn't a refusal to accept new technology for me otherwise I'd still shoot film. When you deal with newspapers, magazines and foreign countries digital uploads are the only way to go. For me the CF cards are more practical and are pretty indestructible. When you're on the run, shooting, changing cards in a hurry, they get dropped, thrown in pockets, laundered and I have had the SD cards break or quit working under these circumstances. Trust me you can find them easier on the ground, in the sand or in the dark a lot easier than SD cards. The only time I have ever lost photos on a shoot was either a broken card or I bought a cheap card. Lost a whole football game on a PNY CF card one time. Never bought one again. Whatever card you go with get the best you can buy. They'll last forever. I do like the pin base on the SD card camera plugs though as they are less prone to bending than the CF cards are. It hasn't been a problem in camera but card reader adapters are less forgiving.
CF cards are still faster than SD which as mentioned before show their strength in burst shooting mode, a feature primarily used by professional photographers. CF now has a newer iteration I believe referred to as Cfast 2(If I got the name wrong feel free to correct me) that has write speeds of over 500 MB/s allowing it to do high speed continuous without ever needing to stop for buffering. I've also heard many mentions of SD having a higher corruption rate than CF, so there is a bigger feeling of reliability. How much of that in anecdotal in regards to reliability vs demonstrable is a question though that I do not know the answer to.