Sustanon is quite a serious supplement, I've only ever heard of bodybuilders taking it.
Benefits are apparently it's a mix of testosterone which gets released at intervals or something like that.
It uses different esters with the idea of releasing quickly and then over longer periods. While in theory it sounds nice, many of the hormone clinics no longer favour this or nebido as it can be difficult to manage the peaks and drops. You do get the benefit sometimes of fewer injections.
In the end its all exogenous test, but the big thing with this is managing consistent stable levels as much as possible