i would say dump the myvi as soon as possible if you don't like it. The way the market is now, the longer you hang on to it, the higher the likelihood of you loosing even more. There is still a high demand for the myvi, so getting a reasonable price for it isn't quite hard.

The Swift would be the obvious choice because it is new. While Peugeot makes good cars, there is always the risk involved in buying a second hand car, and spare parts for a continental car like the Peugeot is not cheap, nor easy to find. I for one would recommend peace of mind anytime over loosing a few thousand ringgit. Once your one year warranty on the Myvi runs out, you'll be forking out even more to get the faults repaired.