Hi there, Alec.
I see that you're wanting to find an iPhone with similar display measurements of your iPhone 6s Plus. The problem is, the measurements for the display isn't listed in the technical specifications, and I'm glad to help with this.
Identify your iPhone model -- This article lists the different models of iPhone over the years with a link to each model's technical specifications. Since the size of the display isn’t measured out, you can use the height, width and depth of the different models to find one of similar size.
The technical specifications below seem to be similar in size to an iPhone 6s Plus.
iPhone 6s Plus - Technical Specifications -- This is the height, width and depth of an iPhone 6s Plus.
Size and Weight2
- Height: 6.23 inches (158.2 mm)
- Width: 3.07 inches (77.9 mm)
- Depth: 0.29 inch (7.3 mm)
- Weight: 6.77 ounces (192 grams)
iPhone XS Max - Technical Specifications
Size and Weight2
- Width: 3.05 inches (77.4 mm)
- Height: 6.20 inches (157.5 mm)
- Depth: 0.30 inch (7.7 mm)
- Weight: 7.34 ounces (208 grams)
iPhone 11 Pro Max - Technical Specifications
Size and Weight2
- Width: 3.06 inches (77.8 mm)
- Height: 6.22 inches (158.0 mm)
- Depth: 0.32 inch (8.1 mm)
- Weight: 7.97 ounces (226 grams)
Take care.