German phrase
Welche ~ vergleichen Sie?
Meaning
Which ___ are you comparing?
When to use it
It asks what is compared. Use it politely in shops or meetings.
Example dialogue
Ich kann mich zwischen dem roten und dem blauen Kleid nicht entscheiden.
I can't decide between the red dress and the blue dress.
Welche von den beiden Kleidern vergleichen Sie?
Which of the two dresses are you comparing?