Just completed a stay here (against a stay at the Hilton down the road).

Pricey to get here from airport (25 Euro taxi). It'll be 20 Euro to the Hilton... that's the taxi minimum when departing the airport. Not worth waiting for the hourly shuttle imo (unless you get lucky). Good news is they have Uber going back to airport... around 10 Euro. At that price, no need to deal with their hourly shuttle imo.

Giant hotel. Base room is tiny and dark. No design whatsoever. Quite a disappointment. However, second stay I was upgraded to a suite... absolutely lovely. Stunned at the difference in the two rooms. If you get a suite upgrade, you'll be quite happy at the Marriott for sure. Hilton has much nicer base and executive rooms (with a boutique feel). Pillows in the Marriott are decent but nice and soft at the Hilton. Beds at the Marriott are above average due to the pillow top (Hilton beds are extremely hard). F&B at the Marriott is excellent. Breakfast is a large spread in a giant hall (or you can have the small private version in the exec lounge). The exec lounge is very nice offering lots of food during all hours and adding hot version during the evening times (5:30-7:30pm). You can definitely make a meal out of it on some nights. On others, not as much. But a very large snack can be had for sure. Hilton exec lounge in comparison is a complete joke. Don't bother staying over there for it.

Marriott has a nice usable gym. During my stays the Hilton was more expensive than the Marriott by a lot (50% more). Of course ymmv depending on when you go.

Personally I'd choose the Marriott 9 out of 10 times after having done both hotels. I'd only choose the Hilton if I had a 1 night stay, their rates were cheaper, and I didn't expect to be able to use their F&B due to flight times. Or if I was traveling with the gf and she strongly preferred light & design (again their base rooms are much nicer). The one negative, and it is a biggie, is if I were placed in a base dark room with nothing in it (no design element at all) at the Marriott... it'd be annoying. But if I expect to eat breakfast and use exec lounge and am just here for 1 night, I'd deal.