New boots too stiff?

You'll be fine, just focus on keeping your shins up against the tongues of the boots so you dont get in the backseat. It may be weird the first few times out but it will begin to feel natural after a while.

VolkswagenI bought a pair of Salomon x pro 120s yesterday. I worked with a boot fitter to make my choice. Before now I have only worn rental boots, which I've read are usually very soft. When I did some reading online on the boot I purchased it is recommended for advanced or expert skiers. I can do 360s and box slides, but I am definitely nowhere near being an expert. The boot is very comfortable, seems to flex fine enough, and fits great. I'm just wondering if my new purchase is going to have me falling all over the hill the next time I go skiing? Should I return the boot or get the boot softened or is a 120 flex no big deal? I'm 5'11'' and 170 pounds. I enjoy skiing park mostly.

One of the major failings of the ski boot industry is the marketing behind the boots- it is super old school in that it tries to match up the skier level with the flex/fit of the boot. These aspects are 100% independent from one another, so don't get hung up on the boot being for "advanced or expert" skiers. If the boot fits you and is the right flex for your weight, strength, and preference, then you will have an awesome boot.

onenerdykidOne of the major failings of the ski boot industry is the marketing behind the boots- it is super old school in that it tries to match up the skier level with the flex/fit of the boot. These aspects are 100% independent from one another, so don't get hung up on the boot being for "advanced or expert" skiers. If the boot fits you and is the right flex for your weight, strength, and preference, then you will have an awesome boot.

80's ski shop: "How good at you at ski racing?"
Skier: "I don't race."
80's ski shop: "Here's a racing ski, it's all we sell anyway."

Lather, Rinse, and Repeat for boots.

If your choice is between the 120 and the 100 I definitely think you made the right choice. At 170 lbs and presumably improving over the next few years I think you'd be flexing through the intermediate boot, and it may not even occur to you that your boot was too soft since that's what you're used to with rentals.

I have the same boot. I bought it in April of 2015. At the beginning of that season I was a terrible backseat skier who had never taken a lesson. At the end of that season, I was a terrible skier who had taken one lesson, but learned that I was supposed to pressure the front of the boot/ski at the top of the turn. The following year I trained and got PSIA certified. The better I got, the more aggressive I got. I ran into some problems with shin bang or coning. I have very thin legs, I'm 6'1" about 165. I was experiencing pain on my shins around the power strap. I was pushing the boot and the power strap was the only place I was getting contact. I saw a boot fitter and he put a Booster strap in place of the power strap. It is stretchy neoprene that gets tucked behind the shell of the boot. It solved my shin pain and allowed me to feel a nice flex in the boot while maintain contact along the whole shin. It was $40 and worth every penny. It might be a good route to go if you decide you want more flex. I also bought a custom footbed. I'm not sure which deserves the credit, but between the two, my world changed overnight. Now I'm trying to decide whether to get a new liner since my old one is packed out with over 200 days or to get new boots altogether.

Park skill has ZERO correlation for the most part to actual skiing ability. Its more gymnastics than skiing...which is fine its fun as hell and takes a lot of skill to be good at. That being said...a 120 + boot is going to be way more responsive than a soft boot. Once you get used to it you will never be able to flex down again to a softer boot its like riding noodles