Really depends on what your plans are.

Which RI? The one on Peel or Westmount? Peel would be more central location. RI Westmount is in a more residential neighborhood but is walking distance to Atwater station. Like other Residence Inn, it's more marketed more towards extended stay. Westmount did proactively upgrade Platinum.

CY is near Chinatown and walkable to Old Port. Platinum get a F&B credit. It's "newer" of the three here.

Don't know what the lounge status at DH is. Elite Breakfast was also available at restaurant but it's a pretty weak offering. I often times skipped the free breakfast as it was that bad. Delta did renovated a couple of years ago.

I don't think any of these and other Marriott/SPG locations are out of the way. It's either walkable on a nice day or have access to subway.