I was using Jan Marini's C-Esta product for about two months because it was one of the most stable proven vitamin C products out there in a great consistency. I was a little unhappy with the added Fragrance and parabens in the c-esta though. One of the two ingredients either the fragrance or parabens created some mild stinging.
My main reason for switching to Dermaquest's C product was that is was paraben and irritant free. Not to mention is has more forms of Vitamin C, DMAE complex, more antioxidants, calming agents, and Idebenone, which is Prevage's key ingredient. All this in a very stable form of vitamin C. No worry of oxidation before it arrives at your door.
I've only been using this one for about two weeks now, but I can already see additional pore size shrinkage from this over the C-esta. I also feel like it lifts and plumps a tad more too.
One other advantage I like over the c-esta i mentioned before were the additional anti-oxidants which will really help give some additional protection when your out in the sun.
I highly recommend this as a go to Vitamin C product.