Having actually lived in both places I must say that I love the Midlands.
The Western/Southern Cape is highly over-rated. The weather is dire. Winters are cold, sodden, damp miserable affairs. It is also remarkably humid. In Summer you need to deal with permanent gale force winds blowing dust and dirt everywhere. The people are also unpleasant and the people seem to be infected by a perverse wannabe-gangster mentality. There are ridiculous levels of drug related crime and general petty criminality. The place is also becoming an over-priced tourist trap with stupidly overprices restaurants and B&Bs with poor service and quality catering to Dollars and Euros.
The midlands on the other hand have real weather. Gin and Tonic still Winter days. Warm dry Summers with evening thunderstorms that leave everything feeling refreshed and cool. The people are down-to-earth and friendly. Everything is reasonably priced and you have stunning landscapes. You're a day trip away from accessible beaches and mountains that aren't swarming with obnoxious tourists and overpriced bistros selling last weeks fish.
So, erm, yeah. I think I'll keep my vote for Howick or Nottingham Road.