The Alienware AW2521H, just like the Asus ROG Swift, uses 360Hz on a 24.5 inch screen. The IPS panel is manufactured by AU Optronics, it’s probably the same panel. Dell doesn’t yet state a resolution, but this is probably also 1,920 x 1,080 pixels. To prevent tearing, G-Sync is supported.
So far, only monitors with up to 280 Hz are on the market. The Asus monitor announced in January is also not yet available. However, the market launch of the 360 Hz monitors can still be expected this year.