Depends on your current setup. I'd offer you my insights of the pros and cons and let you choose which would fit you best:
2x 24" 1080p PROS:
- You can do simultaneous programs in full screen (such as gaming on one screen and movie/web browser on another)
- The "windows' are physically segregated (by each monitors) which sometimes help in multi-tasking organization
- You'll probably game in just 1 monitor, so, a lower GPU requirement in running 1080p gaming
- Desktop fonts/sizes appear bigger (readable) in 1080p if monitors are distanced further away from where you sit
2x 24" 1080p CONS:
- Takes up more desk space (not ideal if you have a small desk that already includes space for your chassis, speakers, etc.)
- It's awkward to game in both screens having bezels/border in the middle
- Great chance you're head is always tilted one way or the other (depends on how you place the 2 monitors)
- Slightly angled monitor/s may produce uneven colors if TN panels are used (may be forced to get 2 IPS monitors)
- In your linked price, will cost more at $240 per monitor x 2 = $480.
1x 27" 1440p PROS:
- Takes less space in your desk / cleaner setup / less cable clutter
- Full front viewing / less strain in the neck and may opt for TN, VA, or IPS panels (wouldn't matter much due to direct viewing)
- Higher resolution offers more screen real estate and better quality especially when using certain programs or games
- Physically, a much larger screen size than the 24" (helps when viewing movies from afar, away from your desk).
- In your linked price, will cost less at ~$459.
1x 27" 1440p CONS:
- More taxing to run with your GPU due to more pixels compared to 1x 1080p (requires powerful/expensive GPUs)
- No pysical separation of windows as multi-tasking work will be via 1 screen (but will have more space due to higher res)
- When gaming on full screen, no other programs are visible
- Desktop icons/texts will appear smaller (need to increase font size or have to position monitor closer to be readable)