When it comes to the question on which one is profitable then it would really be depending on your risk appetite.
Why? If you are willing that you would really be risking out on accumulating Bitcoin and turns out that the price had risen up
then it would really be a win-win situation yet the profit you do able to earn did really able to increase its price on which means that a double profit for you.
Whereas if you are really that tending to make pair with a stable coin then it would really be just that fixed. If you are that someone who is really that
loving on securing things then this would really be your preferred spot. You could really be able to save up yourself with volatility if you do have Stablecoin pair.

Its up to your own choice which pair you would really be taking because if you do want on having that fixed profit then you would be sticking with USD
since its value is really that fixed but if you are someone whose accumulating Bitcoin then btc pair would be your best shot.
it would be all according into your preference or something that you are dealing with.