Here are my thoughts on T4 alone, i feel it is a bit more muscle sparing, and has synergy with growth hormone. a lot of us are using GH for dieting, health and muscle growth and lately T4 has found a bit of a niche for those using GH and dieting.
T4 has become more and more popular for use in cutting cycles which include Growth hormone.
I would venture to say more and more bodybuilders use T4 today when using GH.
I also feel that T4 is less harsh on muscle tissue and your able to maintain more muscle when dieting down by using T4, than compared with when they’ve used T3.
So using it alone I feel is even better for long term fatloss if you have patience for it to happen, I do not think you need GH with it for general fatloss either and to me it is better on muscles then T3
Just my thoughts