I've moved from Hilton Diamond (gifted initially by VA, then earned) and elite in Club Carlson and a few other schemes to moving everything to Hotels.com for the last few years. I'm not sure if I am imagining it or not but now I am Gold at Hotels.com I do notice more sale prices that often aren't available if you look through aggregators (they do say you get access to "special prices", but I just assumed that was spin, there seems to be some truth).
The variety is better (in fact, one of the reasons I moved from HH is because the lack of options in many places I travel to!), and quality is generally good (of course do your homework). You don't get a suite upgrade but you don't get penalised either - I have not ended up with the basement yet (fingers crossed). For someone like me who just needs a clean and comfortable bed, a central location and free and fast internet it works well. Mrs G also appreciates that we can use the Rewards to go somewhere to reconnect after all the travel I do for work!
For the hotels I use I generally find it cheaper (but others like Agoda can be better as well), and the rewards are probably the best "value" n $ terms you'll get. The 10% (technically 9% due to GST in Australia) is pretty good, and if you use a cashback reward site you can get up to another 8% back (we use it to keep up our US bank account topped up via Ebates as they often do double-cashback promotions at 6-8%).
The "10%" and cashback rates are on hotel prices only, not taxes and fees. You do need to pay taxes and fees if redeeming too (so in Australia you would need to pay GST component).
I do maintain other memberships, and I would never use Hotels.com if it was more expensive than elsewhere (although, I have once or twice used it when it was just a couple of dollars more as I worked out it was cheaper once cashback and rewards were factored in).