What are the pros/cons of using symmetric crypto vs. hash in a commitment scheme? In a commitment scheme, are there any differences on using a symmetric cipher versus using a hash? 

If at the "opening", I have to reveal $r$ (a random number concatenated with the messaged at the time of hashing) and $m$ (the message),  why not reveal the key used for encryption for everybody to decipher the message and so confirm it? 

It seems to me that both binding and hiding properties of the commitment would be preserved? Is this so?

Any pros/cons of using one over the other that I'm unable to see?
My preference would be to use hash for this purpose.
Cons of using symmetric cipher include:


Symmetric cipher keys are shorter than hashes (128-256 bits), where as hashes are longer (160-512 bits).
When considering the length of symmetric cipher output, it is commonly short (like 128 bits). This length is often inadequate to protect against birthday attack and other attacks applicable.
In most uses of symmetric keys, related key attacks are of lesser consideration. However, in this scheme, malicious party could try to use related key attack to find key matching slightly altered message and/or different r. The strongest known related key attacks against AES are $2^{189.7}$ (AES-192) and $2^{99.5}$ (AES-256). These attack complexities are from Wikipedia.


I'm not aware of significant benefit symmetric cipher would provide in this context, except that AES is faster to execute on (many) of recent processors than hashes of the SHA family.