I don't have any scientific proof or articles about Sustanon vs. Nebido/gel but I've been on all three T variants, gel > Sustanon > Nebido. As much of a hassle as applying gel daily was, in retrospect, Sustanon was worse.
Of course it varies from person to person but for me, Sustanon caused my levels to fluctuate a lot. I felt like crap the day before my shot and my temper flared up. Also, Sustanon gave me the worst acne ever and I still battle with the aftermath of it.
Gels keep the T levels more stable as does Nebido once a regular shot schedule has settled in (the shot intervals are so long that it might take a while).
I personally like Nebido the most. I have only four shot days in a year, every 12 weeks. It is expensive, though, with no covering one shot is ~140€ (basic covering brings it down to ~90€) but since I have the special covering these days I pay only around 5€+needles and syringe. I don't know how big the price tag is elsewhere.
Going on Nebido also brought my acne down to manageable level. With Sustanon it didn't matter what I did to my face.
Might be completely unrelated but since going on injectable T (don't know which one caused it) but I can't tolerate chocolate these days as it causes my acne to flare up. I apparently react to the fat in it as I can consume dairy products otherwise with no worry.