All spg / Marriott properties are ok in Warsaw except the Westin and CY at the airport.
Had very good experiences in all of them, including the Marriott.

i don’t like this Westin at all.
Upgrade is a win or lose. No consistency (ambassador status).
Bar is below average. Restaurant is a noisy cantina.
They often have events on the first floor and the whole lobby and hotel is noisy.
Not impressed by the rooms or suites.
They sell for cheap at checkin the lounge access during the week end so the lounge is a zoo and can be hard to find a seat etc.

Sheraton is nice and the renovated rooms are great. Good lounge and love the bar with live music there.

Marriott is a big one and little dated but they have smoking rooms and consistent with upgrade. View is stunning too. Good roof top bar and huge lounge (same they sale so it can be super busy during week end).

I like the Marriot location and the boutique atmosphere of the sheraton. Westin not an option for me anymore after few tries.

The luxury collection is nice but way overpriced in my opinion.

The new renaissance is a perfect airport hotel walking distance from terminal. I would avoid the CY if you don’t want to fall into depression.

For long stay Marriott is convenient for laundry because of the great laundry shop inside the adjacent mall. They are cheap and very professionals.

returning guest plat premier ambassador got suite. You can try they are not bad when asking. I asked the first time and since then I got the same suite assigned. Smoker.