I currently have the previous raspberry pi class 4 card. I'm considering getting the new raspberry pi model 2 class 10 card. Is there a speed difference between the two cards?
Somewhat contra Jivings and Jacobm001, here's a test of two particular cards (class 4 and class 10) I did when I first got a pi:
There is a link there to anecdotal results from other people doing the same kind of test with various cards. Obviously on average class 10 cards are better but the max read speed of the SD card reader on the pi is 25 MB/s, regardless of how fancy a card you get. I believe both class 4 and class 10 are capable of this.
If you are already getting 20 MB/s read, that is something to keep in mind. Again, a class 10 will be better and is probably worth the few bucks in price difference.
The difference between the class 4 and class 10 would be extremely obvious on the original RPi, and even more so on the RPi 2.
Even if you're using a read only filesystem, the boot time will be dramatically shorter.
The class of a Micro SD card determines it's write time, NOT it's read time. Class 10 cards usually have a slower read time than Class 4 cards. Class 4 has a fast enough read and write speed for most everything the Pi does, Class 10 cards can have slower boot times, but you should be fine with either.