Depends.

The Edition is the former Berners hotel with very small rooms (not kidding). You won't get points for incidental spend at Edition. Since you're Silver you won't get free brekkie or i-net at either property (unless you get an upgrade at GH). Edition is Marriott's attempt to be like an Ian Schrager hotel & they're definitely going for the trendy. I think they opened in time last year for London Fashion Week. Whether you fit in depends on if you yourself are trendy It does have a good location vis a vie Soho & Covent Garden.

Grosvenor House is larger & more elegant; definitely not trendy. While it might be a long shot with silver status, you might be able to get an upgrade to exec level which would get you free access to the exec lounge with free brekkie & evening drinks/munchies (although the exec lounge is closed until end of June for renovation & brekkie is in the restaurant). You do get points for incidental spend. It's in Mayfair/Hyde Park area, about a 5 minute walk from the Marble Arch tube stop/Oxford St & 10 min walk from Hyde Park tube stop.

Quite frankly both locations are fine for doing tourism things. You're in Zone 1 for both, both have access to tubes & neither is that far away from the tourist sights. One is in a somewhat more noisy neighborhood; the other in a more quiet neighborhood.

Here's a trip report for the Edition:

Trip Report - Edition London

Here are trip reports for Grosvenor House:

Grosvenor House, JW Marriott Trip Reports

Separate note to Travelreviewguy - Welcome to Flyertalk!

Cheers.