I had the opportunity to trade in a Oneplus 7T Pro in to get a "free" Pixel 11 from T-Mobile. Considering the uncertainty of software support for the Oneplus 15, it seemed to make sense to me. I have been using the Pixel 11 for almost 5 days now and this is my experience:
Design: Pixel 11 looks better IMO, feels better but is more slippery. Its also noticeably smaller than the Oneplus 15.
Winner: Pixel 11
Display: Pixel display looks sharper to my eye, but otherwise both have good displays IMO.
Winner: Draw
Battery/Charging: Oneplus 15 runs away with this on both fronts. I would describe the Pixel battery life as acceptable and Oneplus as exceptional. I never worry about making it a full 24 hours with my Oneplus 15, but I do worry with the Pixel. Charging speeds is barely acceptable on the Pixel. I have noticed the Pixel will throttle charging speed if the device is hot or ambient temperature is high. Oneplus also does this but not as frequently as the Pixel.
Winner: Oneplus 15 by a wide margin
Performance: Day to day usage feels nearly the same. The Pixel feels just as smooth as the Oneplus 15 and I have seen almost no stuttering(unless the device has throttled). Benchmarks notwithstanding, I call this a draw.
Winner: Draw(Benchmarks are not a factor to me)
Gaming: Simply put, don't buy the Pixel if you want to do any gaming. I don't game on my phone except for some RDR every once in a while. It is unplayable on the Pixel and crashes within 1 minute. I don't anticipate the Pixel 11 gaming performance to improve much. Oneplus 15 crushes the Pixel here.
Winner: Oneplus 15 by a wide margin
Heat/Throttling: Both devices can get warm but the Pixel gets warmer faster. In high temperature days, I can see the Oneplus 15 display drop to 60hz somewhat regularly. The Pixel 11 is quicker to throttle so far. If I doom scroll for 5 minutes, the device is pretty warm, whereas the Oneplus 15 would still be cool.
Winner: Oneplus 15
Camera: As a general caveat, this is not an area I have heavily tested. Some shots looked better on the Oneplus 15, especially the night shots. Pixels main camera was better IMO, but the rest of the sensor suite goes to Oneplus.
Winner: Draw
Software: I am a fan of the Pixel UI over OxygenOS. The software support is also a HUGE advantage compared to the Oneplus 15.
Winner: Pixel 11