T3/t4

I have no experience in using T3 or T4 but I would like to experiment with these drugs for my next comp. My problem is that I hear some use T3 while others use T4 and some flip flop from one drug to the next.
How would I know which is the best to use?

I've used T3 at 50mcg/day for years. I don't have experience with T4, I never had issues just using T3 and it did wonders for me.