There is no good and convenient option. Especially on weekends.
GO Transit option is probably faster on weekdays, but it comes at the expense of being more expensive by close to $4. It also is only a valid option on weekdays. You're at the whim of the 1X, which stops at Aldershot GO, actually being there and going East. And don't even think about doing the 1X on the weekend-- because it doesn't run. Nor should you expect to do the 1X after 7pm, either-- it stops running and goes on Plains Road only.
Best bet is probably to get downtown on anything (B-Line is fastest, weekdays only) and take the 101. It skips Aldershot GO. 1X will take a few minutes longer. After 7pm, and on weekends, it will just be the 1 (East).
You will want to ask the HSR driver for a transfer. If you're in and out fast enough, you may be able to avoid the Burlington Transit fare; otherwise, you'll be out $2.70 (PRESTO)/$3.25 (cash).
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