Honestly I have never had an issue with Sust, at all really, I love the stuff! No more soreness than any other test I have used. Occasionally (for some reason only on the lower area of the quad on my right leg, and I cycle between upper and lower exterior quads on both legs) I have had the oil on the needle (I always make sure I push the air out and let a couple drops run down and lube the needle) sting when I stick the needle in, and I can feel a little heat develop, but this goes away pretty quick (less than 10 minutes) after injection. Sustanon was great for me, it never hurt, and also in my opinion I strongly reccommend the 25g needle, length is your choice but dont go less than 1".
The 25g is narrow, but to me that keeps you from injecting too quickly, it doesnt hurt more to leave it in longer! Plus it produces very little scar tissue, and another bonus is that the 'hole' it leaves is much less likely to allow oil/blood to leak back out of the injection site. I have only used 22g, 1.5" needles to inject besides 25s, and to me they are longer than they need to be, and the longer the needle the more distance the tip sweeps around from movement (simple physics!) reletive to the "axis" where the needle meets the skin surface... which means more scar tissue and soreness causing tissue damage. When I was using the 22s (because I ran out of 25s and had a ton of syringes with 22gs already on them) I noticed that when I pulled the needle out, even at full depth a lot more blood and oil would drain out than I was used to... It would make me mad cause it seemed like so much oil! Normally I would get maybe a single, tiny, drop of blood after injection, but with the larger needle it would be a deep red spot the size of half a dime or a dime on the alcohol pad (I always hold a fresh pad over the injection site while I massage it). It wasnt a lot, really... but it felt like I was wasting a ton!!
If I were you I would just take a few more deep breaths during your inject and use the needle that hurts less (they both feel about the same), scars less, controls delivery, and looks a lot less scary!! Just my two cents!