I am against' 27 inch monitors. It's just not quite as good as 30". I have a legit reason.
Viewing distance.
On 27" you get the high resolution and all, but due to the size and High DPI, you still have to sit "quite close" to the screen.
On a 30" you can get a Very comfortable "meter" away from the screen, still be able to read everything.
Some younger kids might not notice this, but focusing close up requires your eye muscles to contract, while looking into the distance relaxes them. The further away from the monitor the better.
And the price is really a non-issue since it'll likely be the last monitor you need to buy for YEARS AND YEARS.