I'm pretty sure I missed the early wave of choonsas (sweet mangoes from Pakistan), but I did get some yesterday. I don't know this with certainty, but I believe a Pakistani person would tell you these are the best mangoes around. An Indian person would tell you they are super sweet, but lacking the depth of flavour and perfume the Alphonsos offer. I would tell you, they are definitely delicious and worth trying.
My in-laws picked some up yesterday on Gerrard St. They are slightly better value than Alphonsos. A box of 8 cost $12 (vs. around $24 for 12 Alphonsos).
Oh, another thing about choonsas, I believe the quality is more consistent.