reason for choosing it - want to make it short as much as possiblexxforyy.com?
The second one is less spammy looking to me. I personally don't like either BUT I've seen an increase in exact match domains in the first pages so you cloud give it try...Lets say there is keyword like best XX for YY.
What makes better EMD?
bestxxforyy.com
or
xxforyy.com?