UP Express train to Union StationorBus 900 and subway to Union Station?

The short answer

For one traveler the Bus 900 and subway to Union Station is cheaper by CA$5.95. That does not change up to 8 travelers.

The UP Express train to Union Station is quicker: 28 min against 45 min.

UP Express train to Union Station: 05:27–00:54. Bus 900 and subway to Union Station: 05:22–01:10.

Priced against each other

Whole-party totals · adult fares

What each costs for the whole party, in CAD. The cheaper of the two is marked on every row.
Travelers	UP Express train to Union Station	Bus 900 and subway to Union Station	Difference
1	CA$9.25	CA$3.30	CA$5.95
2	CA$18.50	CA$6.60	CA$11.90
3	CA$25	CA$9.90	CA$15.10
4	CA$34.25	CA$13.20	CA$21.05
5	CA$43.50	CA$16.50	CA$27
6	CA$50	CA$19.80	CA$30.20
7	CA$59.25	CA$23.10	CA$36.15
8	CA$68.50	CA$26.40	CA$42.10

Where each one leaves you

UP Express · UP Express (Metrolinx)UP Express train to Union Station

Tap on and off with the same card or phone: a different one is charged as a second trip.

Card taps pay the adult fare only; a senior, youth or student fare needs a PRESTO card set to it.

90021 · TTCBus 900 and subway to Union Station

From: Terminal 3 arrivals level, columns C8 to C12, or Terminal 1 ground level, column R4
To: Union Station, on Line 1 of the subway
Runs: 05:22–01:10
Journey: 45 min

Change at Kipling from the bus to Line 2, then at St George to Line 1 southbound for Union.

Tap the same card on the bus and at each subway gate, and the changes are free for two hours. Paying cash, ask the driver for a paper transfer.