どっち（どっち）— which of two; which way (casual)
海 と 山 と どっち が 好き ですか。
Which do you prefer, the sea or the mountains?
どっちどっち
which of two; which way (casual)
どっち
accent [1]In detail
Words
海umisea
とtoand (first option)
山yamamountains
とtoand (second option)
どっちdotchiwhich of the two (casual)
がga(marks the choice being asked about)
好きsukiliked
ですdesu(polite sentence ending)
かka(question marker)
どっち is a casual form of どちら. It asks which of two options here, and can also ask which way to go.
Coco-sensei