You are sacrificing power for mobility and playability with the Steam Deck. I own both a Steam Deck and a gaming PC, and I use each for different games. These days, modern AAA gaming often can’t run on Steam Deck well, including some hits like Baldurs Gate 3 (in the 3rd Act, the rest is fine). However, 75% of my overall gaming time is on the Deck these days. The ability to turn it on and just start playing on the couch or in bed is fantastic, and the support for different control schema like gyro and touchpads make it incredibly playable.
A modest PC is going to push better graphics and higher refresh rates, and will also make some games actually playable, but this becomes a decent sacrifice in mobility and convenience.
If mobility is merely a bonus and your deck would be docked the vast majority of the time, I’d go PC, but I suggest seriously considering the convenience of portable play even within your home. The OLED screen is wonderful for years-old AAA games that go for 2 dollars on Sale, indies, and more. I’m absolutely having a blast with Crosscode and intend on moving over to Another Crab’s Treasure and Nine Sols next.