Well the construction in Sarnia is simply widening the highway. The 402 will have 4 westbound lanes when done next year (eastbound will remain 2 lanes). This will help ques for the border crossing.
-I think either one or both of those new lanes will be strictly for truck traffic. Separating them from travelers and Sarnia commuters will make the route much more efficient.
Far and away the project in Windsor is more massive. Here's a video I took of the 402 in Sarnia over the summer showing the construction:
• Video Link
Compare that to what is being done to the 401 in Windsor:
• Video Link