Seems like the H version only has HDMI x2 and VGA whereas the Q has HDMI, VGA, DP and DVI-D. H has better contrast ration but probably not noticeably so.
Other than that
Why do ASUS need 4 monitors in the same price bracket:
Asus VE276N 27" Widescreen LED Multimedia Monitor - Black
1920x1080 Resolution, 10000000:1 Contrast Ratio, 300cd/m² Brightness, 2ms Response Time, 1x Analogue Input, 1x DVI-D Input, 3 Year On-Site Warranty. Asus10+ in stock £199.99 (£166.66)
Asus VE276Q 27" Widescreen LCD Multimedia Monitor - Black
1920x1080 Resolution, 100000:1 Contrast Ratio, 300cd/m² Brightness, 2ms Response Time, 1x Analogue Input, 1x DVI-D Input, 1x HDMI Input, 1x DisplayPort, 3 Year On-Site Warranty.
Asus10+ in stock £229.99 (£191.66)
Asus VE278H 27" Widescreen LED Multimedia Monitor - Black
1920x1080 Resolution, 50000000:1 Contrast Ratio, 300cd/m² Brightness, 2ms Response Time, 1x Analogue Input, 2x HDMI Input, 3 Year On-Site Warranty. Asus8 in stock £239.99 (£199.99)
Asus VS278Q 1MS Gaming Widescreen LED Monitor - Black
1920x1080 Resolution, 800000000:1 Contrast Ratio, 300cd/m² Brightness, 5ms Response Time, 1x Analogue Input, 2x HDMI Input, 1x DisplayPort, 3 Year On-Site Warranty. Asus10+ in stock £239.99 (£199.99)