Unless you have family or business in these areas, and if your focus is to visit Toronto, you won't save much by staying outside of Toronto, in time or money.
Perhaps if you provided a bit more info...
Well, this is a leisure trip. I picked those areas because that's where Staybridge suites are located and they have kitchenettes. I would prefer to cook my own meals at times. I plan on renting a vehicle and doing a lot of sight seeing .
There are suite hotels in the city that have kitchenettes. However if you only want Staybridge hotels then either the Oakville or Mississaugua locations would probably be best. They are located close to major highways, and have relatively close access to GO transit - commuter train - which can get you into the city quickly and efficiently. Driving in the city itself is frustrating and slow, and parking is expensive. Public transit and walking is the best mode of transportation in the city core.
Well, I'm in the rewards program with Staybridge so Oakville it will be. On the map I see that it is near water, is this a beach?
The southern parts of both Mississauga and Oakville are situated on Lake Ontario, which as you know is one of the Great Lakes. Both towns have lakefront parks, some beach area etc. Oakville has a very nice downtown close to the lake. If you have a car you can get there easily from where your hotel is, but neither the downtown nor the lake is walkable from the hotel.
Holiday Inn is also a part of their rewards program. There are two Holiday Inns right downtown, including one that offers free breakfast. They are much better choices, imo. There are a wide variety of places to eat in downtown, many at cheap prices.
OK, I have one more. Are there any work out gyms close by?
Downtown in which town? No Holiday Inns in downtown Oakville. There are Holiday Inns in Oakville but not downtown.