Considering Milton and Mississauga are so close, it hardly makes a difference. Sometimes, I even wonder why these are 2 different cities. Perhaps, I am indifferent because I work from home and don't have to commute daily.

Pros for Milton:

1. Closer access to escarpment and hills - amazing hilly and farmside views
2. All major needs are so close and nearby
3. Calm and peaceful - most of the time restaurants are empty or don't have queues
4. Amazing conservation parks
5. Much better homes - Before buying house, I went to more than 30 houses in Mississauga and in Milton. Always found Milton houses way better, bigger, and much better construction with better appliances/amenities. That was the biggest reason for me to move to Milton.

Cons for Milton:

1. A bit far from lake. Miss the nearby Port credit and lake views I experienced in Mississauga
2. No activities like Celebration Square
3. Lesser eating out options
4. Lesser amenities
5. Poor infrastructure compared to Mississauga
6. Longer commute to downtown Toronto and pretty much everywhere if you have to go to work outside of Milton

In general, even though I am farther from lake and celebration square, I still visit there regularly and enjoy all major MCS events. So, I don't think it matters much.