EC is an ant, Clen is an ant eater. There is no real comparison.
As far as T3 vs clen... that's comparing apples to oranges. Both are great for fat loss, both come with their respected side effects. It takes a reasonably high dose of clen to start seeing negative sides, and higher than that to damage yourself. As for T3, the thyroid is easily damaged, and it's not hard to mess up your hormones with T3.
But to specifically answer the question, given proper dosing, T3 will shed fat faster than clen.