There is a recent thread that covers speed.  If you take ruby 1.9 and 
compile it yourself, it runs about 5 or 6 times faster.  That should 
cover the speed aspect.

Also, the speed of the language is not necessarily all that critical as 
long as it is more or less enough.  You can always add hardware to cover 
that aspect.  After that it is the usefullness of the language that is 
critical.  There are always changes to be made.  You really need a 
language that can refactor and upgrade quickly and easily.  So, 
whichever language you can use to "git thar the firstest with the 
mostest"  (old saying) that is the one that they should use.

For the record, if your team is efficient and proficient with one 
language and not the other, then go with what you know.  Fighting a new 
language could be a problem unless they can pick it up easily.  Which 
language is better is irrelevant if they cannot use it.
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