I agree, you can never say which area is good or bad. It all depends upon your needs and circumstances. Just a few thoughts from here and there:
Community
Peel region – home to the largest South Asian population in Greater Toronto Area (GTA). South Asians (Indians, Pakistanis, Bangladeshis and Sri Lankans) comprise 18.7% of the population of Peel.
Brampton municipality – South Asians comprise 25.8% of the population. If you go into details, immigrants from India comprise 21% of the population while those from Pakistan are 2.6% and Srilanka are 1.9%. The second largest group is from West Indies 5.5%.
Mississauga municipality – South Asians are 14.8% including India 8.7% and Pakistan 4.4%.
York region – home to a large Chinese community (11.4% of the population) followed by India (3.3%) and Iran (2.4%). Chinese immigrants are concentrated in Markham and Richmond Hill municipalities. Iranian immigrants are concentrated in Richmond Hill where they comprise 7.8% of the population.
Markham – see above
Vaughan – appears to be mixed with visible minorities at 31% of the population. Immigrants from any source country are not concentrated.
Durham – lower number of immigrants have chosen Durham region. The largest immigrant groups are from West Indies (2.7%) and India (2.2%). Both groups are concentrated in Pickering and Ajax. Oshawa is the least concentrated by any immigrant group.
Schools
The best schools of GTA are located in York region (Markham, Richmond Hill etc) and can be explained by the concentration of Chinese immigrants who focus on kids academic achievement. Vaughan lags as there is hardly any elementary school there with a five year avg rating of more than 7.5.
Schools in Peel region are mixed lot with those in Mississauga being relatively better than Brampton. There is hardly any elementary school in Brampton with a five year avg rating of more than 7.5.
Schools in Durham region (Oshawa, Pickering, Ajax etc) generally of low ranking.
House rents
House rents would be a function of house prices. The price of a single-family detached house is the most expensive in York and the cheapest in Durham. Latest benchmark prices are given below:
York region
Richmond Hill $806,700
Markham $745,600
Vaughan $688,300
Peel region
Mississauga $624,500
Brampton $437,200
Durham region
Oshawa $298,500
Oshawa home prices are cheaper but bear in mind that it is a very long commute to Toronto downtown.