New Display technology as well as development and research
I think it mainly is about the response times, tv:s for at least this point havent been able to to keep up fast motion. Also connections are diffrent, sometimes displayport is the better of the two to display image. Things are lot more different now, specially oled ja LG, GSync etc.. Me personally waiting to get the chance to buy LG 48CX, change my 38UC99 for it :D After that i can really make a real comparision. Like some tech site said the diffrecence today to buy tv or monitor is not so big. Just think LG 38" inc monitor, fast 144hz but crappy HDR for 1500-1900e, LG 48 CX 1500€ :D Bigger better image quality, true HDR, fast panel. Burn in ? maybe but use it correctly and use common sense not a real issue. yeah someone can debate about the size but 48" is not bad for 1m or bit more distances, i have about 1,2m maximum seating distance. It is personal taste nothing more :)
The common arguments against using TVs as monitors that you have read here and elsewhere haven't really been an issue for several years. There are two main 'issues', but both can almost certainly be resolved within the settings on your TV.