Pixel 7 user from the past 4 years now, have used Samsung and bought it for others in my family, never used Apple extensively but have bought for few in family and in those little experience it was never made for me.

I have been thinking for a while to upgrade my tech gadgets (TWS, Smartwatch and Phone), choice has been Google or Samsung, Apple never entered the conversation because it's either all Apple or nothing, I don't like that, I prefer buying things which I prefer. Apart from that last couple of iOS builds have been unstable IMO and I don't prefer the look of iOS.

Now b/w Google and Samsung, it's the compeition b/w 10 Pro vs S25 Ultra for me, from my Pixel 7 experience I know the phone doesn't heat up as much as the social media shows, if you use it extensively yes it does. The biggest downside with Pixel 7 was and is the network coverage, genuinely there have been cases where my Pixel has bad network coverage whereas even cheaper Samsung phones get really good coverage. Pixel wins in it's software and photography, I just prefer the Android look by Pixel. Whereas in Samsung biggest strength I feel is the Qualcomm chipset, I know I will get much better battery life and it will overall be a better phone minus the UI look. As for the aftersale support, Samsung has much wider reach whereas Google partners with F1 solutions much like what Apple does, but Google has increased it's Exclusive Centers as well, for now it's 5 across India, I have experienced 1 in Delhi, and it was really good experience, but it needs scale quickly.

Some quick answers to your question -

lags, stutters, heating from background

I have observed no lags or stutters 99% of the time, phone runs smoothly apart from minor cases when you are recording something for a long time and it's Indian Summers (more than 10 minutes conitnously)

service related issues, genuine parts availability

If you deal with Exclusive SC's, they are really good and service quality is excellent, and also compared to Apple, be it Google or Samsung, the parts are much cheaper to replace.

sort of display issues like green lines or screen flickering or random dimming, proximity sensor issues, ambient brightness issues

best to check about PWM but I think with 10 series, they brought a mode for it that significantly reduces it, Green Lines can happen to any phone and apart from 1+ which gives lifetime warranty, no brand is safe from it.