Chromemoly are generally the strongest, ( and most expensive) and are better suited for high RPM use and higher spring pressures. I use TFS chromemoly pushrods in my car. Chromemoly pushrods are usually one piece. Less expensive pushrods will have welded or pressed-in tips. Some of the cheaper steel push-rods aren't hardened, or heat treated, so they can't be used with guideplates, and they are more likely to flex or bend. What you need ultimately depends on your set-up, but if you don't mind paying a little extra chromemoly is the way to go in my opinion.