Hello all!
Initially, I'd like to state that I own both the OnePlus 15 and the Samsung S26 Ultra with the intent of choosing one of them to be my primary phone.
However, that decision is one of the hardest after comparing the two, so I wanted to share my thoughts and experiences after using both for an extended period of time. I know that many people are wondering which one to choose, so I hope this'll help.
In short, both phones are excellent, and you'll be happy using either. I know, it's the safe conclusion, but both have great cameras, great hardware and great software. There's no way around it, but there are subtle differences and nuances you might want to consider.
The S26 Ultra is larger than the OP15, which obviously gives the S26 Ultra the larger screen. This is perfect when consuming media and operating the phone, but it can make it a bit cumbersome to use single-handed. The OP15 feels more compact and easier to use, but the screen is obviously smaller. The Samsung comes with an S-Pen, and the OP15 does not, so if the pen is important to you, the Samsung is the obvious choice.
However, the OP15 is more robust and can handle more abuse than the Samsung. In terms of performance, both phones are knocking it out of the park. It's that simple. Both are rocking powerful chips and more than enough RAM to get the job done, whether it's gaming or high-demanding tasks. On paper, the S26 Ultra is slightly more powerful with its enhanced chipset, but I don't think you'll notice in real-world usage. Everyday usage is flawless on both phones, so you'll be happy with either.
The displays differ, with the OP15 having a slightly lower resolution, which is noticeable in some situations. You'll have to look carefully to really see it, but it's a fact. The S26 Ultra has more pixels on screen to work with, so if resolution is important to you, the Samsung is the way to go. And yes, the S26 Ultra has the Privacy Display, but I sadly feel somewhat ill when using it, and I don't think it's that useful, as the angle has to be quite severe to really make a difference. It's handy in a pinch for some users who'd like to do their banking and other sensitive tasks out in public.
On the flipside, though, the OP15 can, in some games, reach a 165Hz refresh rate, where the S26 Ultra stays at 120. OnePlus has a more vibrant display with more punchy colours. In my opinion, the S26 Ultra has a slightly dull display, even when compared to older Samsung models such as the S24 Ultra. Personally, I prefer the punchy colours on the OP15 to the more natural look Samsung was going for. Furthermore, despite having a lower resolution, the OP15 can at times fit more on the screen, such as menus and options, when using apps, as it can lower the elements displayed more than the Samsung.
Both phones are fine to use in bright sunlight, with the S26 Ultra having the anti-reflective coating, but I've had zero issues using the OP15. Both phones reach a very high brightness, so you'll be fine regardless of which phone to use.
The cameras have been a hotly debated subject, but I think both are much more comparable than the numbers and specs would suggest. Sure, the S26 Ultra offers a more versatile setup, but from my experience, that doesn't translate into much-improved images. Comparing the two, I found the OnePlus 15 to be able to hold its own and even surpass the Samsung in many conditions.
The main difference, from my experience, is how Samsung and OnePlus handle the processing. OnePlus relies heavily on AI and denoising when processing the images, and this can lead to less noise and more details being captured, but it can also lead to objects (especially far away in the background) being a bit messy as the AI can't quite figure out what to do with them. Small text can be a jumbled mess, for instance, and straight lines can become somewhat wobbly.
Samsung, on the other hand, feels more natural and hardware processed, which leads to more noise in the images but better captured details - even in the background. However, objects in the background can also get messy due to the noise, and the AI does not quite understand what it's looking at.
I generally found the OP15 being able to separate objects, like grass and leaves on a tree, (especially in the background, better than the Samsung, but Samsung is generally better in creating a depth-of-field effect.
In low-light conditions, the S26 Ultra has the advantage. The heavy use of AI in the OnePlus 15 can get in the way, and the improved hardware on the S26 is simply better. That doesn't mean that OP15 can't take great low-light images, but Samsung is the better choice.
The S26 Ultra is the better video recorder, in my opinion, although the S26 Ultra can't record in 4K120 whereas the OP15 can. However, the S26 is more versatile and offers a wider range of options when shooting video in terms of options and codecs. If you're into video, you might want to consider the S26 Ultra instead of the OP15. The OP15 shoots great videos, but I miss the options found on the Samsung.
So, the battery. OP15 is the clear winner. Hands down.
All in all, you'll be happy with either one of the phones. They offer a great experience, and I'm genuinely surprised to see how well the OP15 can handle itself in terms of photography. Based on many reviewers, you'd think the OP15 has trash cameras, but that's simply not the case.
Both phones have clear advantages and disadvantages. After using both phones, I can't objectively say which one is the best option. Sure, the S26 Ultra offers a great package deal with long-term support, but the OP15 offers an outstanding battery life lasting up to 3 days on a single charge. I'd say the Samsung feels more refined and is more aimed for the general user who wants a great "jack of all trades but master of none"-phone, whereas the OP15 aims for the power-hungry user who wants the best performance and battery life.
In the end, the Samsung feels more refined and premium to use, but the OP15 simply feels more fun :)
Regardless of which one you choose, you'll be more than satisfied, and I hope this helped you in choosing which one is for you :)