One game away can be as good as infinity with Verlander on the mound and heading back to Houston.
Keuchel is a better pitcher. Verlander can certainly win but given the choice with both pitchers available Houston would prefer Keuchel on the mound in game 6.
Also keep in mind hitters always do better against a pitcher when they face him just days apart as happens in a series like this. Stats show that a lineup will do better against the picture the second time through versus the first and the third time through versus the second. The more they see the picture the better chance they have and in fact do hit him.