Alka-Seltzer PLus was recommended to me a few years back and its the best stuff I've ever taken for colds/flu. You can feel it working within 15-20 minutes. Really good stuff. As far as Ester-C, I try a lot of supplements and was never impressed with it. It just didn't feel right in my body. Regular C is cheap, time-tested and works fine. The Vitamin C foundation also doesn't recommend it.
http://www.vitamincfoundation.org/esterc.htm