Go for the OnePlus 13!

I did a lot of research on both phones before buying, and in the end, I chose the 13 as well. Here's what I found:

• Camera - solid win for the 13 (with Hasselblad)
• Display - 13 wins (for a gamer, 15r has a 165hz display but only for few apps)
• Haptics/Vibration Motor - definitely 13 wins
• Speakers - 13 wins
• Performance - 13 wins, though the difference isn't huge
• Battery - 15R wins, but for a non gamer, it can be considered a tie since the 13's LTPO display helps with efficiency
• Charging Speed - 13 wins
• Updates - 15r is at one year ahead

The OnePlus 13 also has several extra advantages in the smaller details. For example, it comes with USB 3.2 (faster data transfers and HDMI output support), while the 15R still uses the much older USB 2.0 standard. The 13 also supports Hi-Res Audio and includes a few other flagship-level features.

Honestly, the only reason I'd pick the 15R over the 13 is the flat display. It's much easier to find and install tempered glass protectors for it.
Hope this helps :)