I've stayed at all three brands - it really depends on where you're staying, I think. If it's an older Towneplace, I would personally go with a Residence over the Towneplace - however, the newer Towneplaces are nice as well.
Springhill's are good hotels & they do have the microwave & mini-fridge - I think if you're looking for a studio suite & it's less than a 5 day stay, the Springhills are a good options -they have a comfortable layout & the divider that seperates the sitting area & the sleeping area is key.
If its more than 5 days or so, I would personally go with a Towneplace or Residence Inn because of the kitchen factor. The housekeeping doesn't mean much too me because I generally like my privacy - however the TP & RI will both come collect your trash & take care of your towels & toiletries when needed. I like RI's better because they have the full-hot breakfast in the morning & it's definitely worthwhile to get that. I was at a TP once though & apparently they had weekly BBQs for their guests in the summertime which I thought was pretty cool.
If you tell the people here where you're going & how long your stay is, they may be able to offer up suggestions.
Room layouts:
SpringHill Suites
Residence Inn
TownePlace Suites