response time (G2G) results can be misleading. "6ms" isn't necessarily noticeably worse than "4ms" so you need to look at customer feedback and reviews.
I'm having a quick look, but I'd like to say my experience with DELL for monitors has been excellent.
BOTH MONITORS have reasonably good reviews/feedback for the price, though the DELL only has:
1xVGA, and
1xHDMI inputs
If you think you'd want another device hooked up that single digital connection isn't enough. Most people don't but I should mention it.
DELL: https://www.144hzmonitors.com/reviews/dell-s2415h-review/
AOC: https://pcmonitors.info/reviews/aoc-i2481fxh/
1xVGA
2xHDMI
COLOR?
Overall they are both good, but the DELL's gamma etc appears to be better.
My conclusion is...