I've personally tried a ton of different creatine products. The one that has worked the best for me is Kre-Alkalyn (SciFit). I have used Celltech, Cellmass, Higher Power Monohydrate, CEM's, CEE's and Kre-Alk has given me the best results and an added benefits of using 1/2 the amount I was taking in other forms. You only take 1.5-3 g of kre-alkalyn a day compared to 5-10g of the other forms. If you haven't taken it before, I would recommend trying it out on your next cycle.
As for which one gives the best strength, I personally don't believe that any one form is better than the next for strength or size. If you respond well to one form, the other form will likely give you similar affects. Genetics will play the most important role in how your body utilizes creatine and how much is converted to creatinine. This is an added bonus to Kre-alkalyn in that it is pH buffered to ~12 and thus prevents the metabolis into creatinine. Give it a shot and see what you think.