I'm going through this with my woman right now. We've completed first pass on the basic blood panels, and just got back the results. This is the area I just now started to analyze. I put some comments to remind me (since I'm not doing this all at once) where to pursue next.
So to answer your question, it really depends. If your thyroid is performing well, then I'm not sure I'd mess around with either T 3/4. Clen gives me the shakes terribly and makes me irritable, but some can tolerate it better than I. When taking, there is a methodology of stepping up the dose til you are at target dose.
Have you had blood panels to see if any issues?
And what have your "fat loss efforts" consisted of? Do you know your TDEE and are eating below that? Are you doing cardio? How long have these efforts lasted this last time?
Cheers!
---Roman