What's the maximum capacity of storage for Canon EOS 600D and Nikon 5100D?

I'm not sure what it's saying about SDHC and SDXC. But I want to try as 'maximum storage and better performance' as possible.

The maximum storage for the both the 600D and D5100 is a 64GB SDXC… Class 6 cards and above are recommended for video use… Here's an article explaining memory cards: http://www.whatdigitalcamera.com/equipment/advice/517064/understanding-memory-cards.html

It is a better idea to carry a few different sized smaller cards than use your cameras memory card for storage… Memory cards can become 'corrupt' with time and will eventually fail… If you don't back up your images regularly or transfer your shots to your computer and your card fails you will more than likely lose all your images.

I'd buy a couple of 4GB, 8Gb and 16GB cards and use the best sized card for whatever i'm doing with the camera at the time… I actually have over 20 different sized cards in a 'thinktank' memory card wallet…

I always use 8gb cards and never store photos on them for more than a few days if I can help it. It's safer that way in case the card becomes corrupted or lost, you won't have lost everything.

You won't need anything more than a 4 or 8GB memory card. I'd go class 10 though. I have an extra card so I can always have the camera ready to shoot.

Both those cameras use the same class of SD cards so both have the same capacity.

I see advice in the other answers to buy 4 or 8GB cards. High capacity SD cards are so cheap these days that it is pointless buying small ones.
You can't video any file larger than 4GB any way, and it is wise (because SD cards fail) to have 2x 32GB cards rather than 1x64GB. Don't have all your eggs in 1 basket.

For some reason, people think that they can store vast amounts of still and video image files on high capacity memory cards.

This belief can only lead to disaster when a card fails. SD type cards fail much more than CF memory cards, so beware.

The best practice when dealing with memory cards is to copy all the images to a computers hard drive at the end of each shooting day.

Once all those files are safely on the hard drive, format the memory card, using the format feature in the camera.

The only time I use high capacity memory cards is when I'm shooting in dusty, muddy or wet conditions, when changing cards will expose my camera to damaging elements.

4 gb cards are very useful since each card can be copied directly to a DVD, thus backing up everything on the memory card.

The idea of placing all your digital "eggs" in one basket is a bad one. Memory cards are NOT permanent storage devices. They are used to temporarily store files until they can be copied to a computer and later backed up to a more stable system (M-Disc's or cloud storage)

Whatever is the maximum capacity for SDHC and SDXC. It's the technology that matters. Maximum size follows.

Bear in mind that maximum size does not equate to better performance. More often than not, if you don't know how to handle such huge sizes, you will find yourself on the bitter end with lost pictures and corrupted files. With pictures, 8GB is usually enough even for pros.