IPhone 15 vs Samsung S24?

If your main use is photos, the S24's image processing is likely going to be more pleasing straight out of the camera. iPhone tends to go for a more 'realistic' look, which can sometimes be less flattering. Both phones have excellent battery life. The S24 does NOT have a titanium frame (only the S24 Ultra). Ecosystem lock-in is real, so think about your other devices too. If you use a Windows PC, the S24 might integrate better. If you use a Macbook or iPad, the iPhone is an obvious choice.

For your needs, the S24's camera might edge out the iPhone 15 due to its versatility in zoom capabilities and generally punchier colors which are great for social media. Battery life is comparable between the two. Consider that Samsung provides longer software update support nowadays, sometimes exceeding Apple. If longevity is a primary concern, that's a point for Samsung. However, if you're deeply embedded in the Apple ecosystem or prefer a simpler user interface, the iPhone 15 remains a solid choice.

If camera quality for dog photos is the priority, the S24 probably wins with its flexible zoom lenses and computational photography. The iPhone 15 is no slouch, but Samsung gives you more versatility. Battery life tests often show the S24 lasting a bit longer, but it varies with usage; both should get you through a full day with normal use. If you're a heavy user, consider a battery pack regardless. I'd also look at the software each uses: do you like iOS or Android better?