I probably can't help you on a free stays hotels as I believe that is Hyatt/Priority Club offering those. I'll offer my view on Hilton as a recent 'convert'

About a month ago I shifted about half my stays to Hilton from Marriott. I'd been 100% loyal to Marriott for the last 3 years since finishing university with about 150 nights a year on average. Hilton were pretty bad in the status matching department, they gave me a challenge of 21 nights to get diamond (Normally diamond takes 60 nights, or 27 stays). I stay in a hotel about 3-4 nights a week on average so in some ways, if they didn't realise how willing I was to check-in/out, it was quite a saving.

Their earning rate is about the same as Marriotts in standard points, with about the same cost of nights (In my mind I equate them 1 hilton = 1 marriott point). However when I started with Hilton I was receiving a 'double points' promo. This then switched into a extra 1000 points per night and 3x the standard airmiles. As such it means I earn about double hotel points at the Hilton I stay at (which gives around 1000 base points), plus 3000 bmi airmiles (you need 9000 for an economy return in Europe which is good for me, 1.5x that for business). Marriott can't compete in this way as I get hotel points worth about the same in the two chains, but the airmiles are worth quite a lot extra - as was having a choice of two chains when I go on holiday. When I get gold/diamond I'll also get another 1000 hotel points on checking in and as my current pattern is to check-in only for 1 night to maximise on the check-in gifts from the two chains it will also work out nicely.

Having said that I still stay about half my nights at Marriott as they tend to have nicer hotels in my local area and I'm intending to be top tier in both chains. But, it does mean that Marriott will have lost ~80 nights by the end of the year from me.

As for why I switched: I no longer felt that Marriott was offering me a proposition that was too good to go to not try out other hotels. I was disappointed in the end by the increasing redemption cost that eroded my existing points, and Hilton's offer of 'free' airmiles as well as hotel points was very attractive. I haven't really noticed cutbacks in services in the UK - but my local Marriott has dropped from being full each night to being half empty much of the time (it is very business focused).