I think its fifty-fifty u can use both, both of them are common enough, kelime can be Arabic , this is normal because there are lots of word from Arabic in Turkish language because of Religion, Relationships between Arabic speakin countries

We use both of them, new invented Turkish word is ''sözcük'' but the old man is ''kelime'' and Arabic in origin, right.

I feel like kelime is used more often.

you can use both of them

kelime