Why is Rijndael a better encryption method, as compared to DES?
While there is much debate about the security and performance of AES, there is a consensus that it is significantly more secure than even 3DES, and in many environments faster.
The AES is available in three key sizes: 128, 192 and 256 bits, versus the 56 bit DES. Therefore, there are around 1021 times more AES 128-bit keys than DES 56-bit keys.
Some cryptanalysts have also suggested that AES performance is up to 40% faster in hardware and software than 3DES, although it's open to debate and interpretation.
As one expert put it, assuming that you could recover a DES key in a second (trying 255 keys per second), it would take the same machine approximately 149 trillion years to recover a 128-bit AES key.
For some good insight check out the article Do we need AES?