Only difference between the 348 and 349 is the refresh rate is 20Hz higher on the 349. They are both IPS panels and subject to back light bleed. All IPS panels are. I saw people posting how much better the Predator is but guess what, they use the same LG panel. There are some that are just unacceptable but for the most par unless you crank the brightness to max and stare at a black screen in a pitch dark room its not an issue. I had issues with a 348 and pulled it apart and ran some thick super 33 electrical tape around the front perimeter just where the bezel would cover it and problem solved. I noted before I did that when you push in on the bezel it dissipates. So the electrical tape put more pressure around the edges.
Some websites actually put a disclaimer on all IPS panels as they were tired of getting monitors returned. In the beginning New Egg had a massive stock of open box, im guessing multiple returns over staring at a black screen with the brightness maxed in the dark. Seems no matter the technology they all have their caveats. TN panels dont have backlight bleed but crappy color and bad viewing angles. The newer VA panels will ghost until you mess with the settings enough.