Some people love splits, some people think they suck. I think they suck, basically for the reasons you listed; although they do offer good forward propulsion with minimal effort they, from my experience, don't allow for much control. I will tell you that when I switched to a paddle fin (Mares Quattro) I immediately became a much better diver and enjoyed diving more. I honestly was getting so frustrated with my splits I was ready to quit diving...thankfully I did some research on various forums (including this one) and discovered that there were a number of divers who hated splits for the same reasons I did. So, in short, I would definitely give a good pair of paddles a try; they may be just what you're looking for.
Here are some of the paddles that seem to be consistenly well regarded:
Mares Avanti Quattro, Mares Volo, Mares Superchannel, Scubapro Jetfin, Scubapro Seawing Nova, Hollis F1, Aqualung Slingshot. However, the only ones of the aforementioned that I would consider light are the Mares Volo and Superchannel.