In terms of overview main contenders for silverware look to be Los Angeles, Seattle and New England. However, MLS has great deal of parity so never rule out surprise club like a Houston or Dallas or even Toronto coming out and winning a shield or cup. Generally we don't really know until a good 10 matches in how the league is shaping up, especially this year with two expansion sides being major variables.
If I had to predict right now?
West
1. Seattle
2. Dallas
3. Los Angeles
4. Portland
5. Salt Lake
6. Kansas City
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7. Houston
8. San Jose
9. Vancouver
10. Colorado
East
1. New England
2. Columbus
3. Toronto
4. New York City
5. DC United
6. Orlando
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7. Montreal
8. Chicago
9. New York
10. Philadelphia
Revisit this in a couple of months just to see how wrong I am. Again, very difficult to predict as single injury or major transfer can shake things up.