You are probably breaking your wrists on your back cast in an attempt to overpower the rod, leading to your tailing loops. I'm guessing you were fishing in ponds and/or ocean with the smaller rod. I'm also guessing that you're not halting the rod firmly with the smaller rod on your back cast. The small rod probably is a full flex not designed to be manhandled.
I don't necessarily believe the length of the rod will give better or worse loops. You may have to tighten up your technique a bit.