As a Californian I never think about Accor. What are its strengths? Here are the kinds of strengths I would identify in other groups:

Hyatt
-points are a true store of value (for the moment)
-elite benefits are industry-leading (suite upgrade certificates, breakfasts, late checkouts)
-the app lets you see the hotel bill as it unfolds

Marriott
-tremendous scale
-some of their cookie cutter brands are truly cookie cutter — you can close your eyes and wake up anywhere in the world and know you're in a Marriott
-lifetime status is attainable
-that's about it; Marriott can otherwise be really disappointing

Hilton
-you can pick a room and check in all on the app without making any contact
-they basically give away their 'free food' elite status (though kind of a weak status) via credit cards

IHG
-their points can be a surprisingly useful access point to cheap room rates
-they're trying to catch up to Hyatt on the elite side with a little bit of copying
-their Holiday Inn Express brand is truly ubiquitous in the USA though this perhaps overly defines IHG

Choice
-they control the midscale world in places where midscale tends to be branded (USA)
-surprisingly good coverage in Nordics and even Tokyo

Wyndham
-their loyalty folks are willing to get creative and try interesting things
-very strong credit cards

Best Western
-not sure, not a fan, sort of anti-brand
-okay, I guess they can be decent in European city centers where no one else exists