Again, it doesnt depend entirely on the phone or what you are loading. You could have excellent coverage but if you have a lot of competition for the internet with limited resources for sockets or bandwidth on your area, it won't download as fast. For example, in my apartment I get only 3 bars of signal, but I can watch videos on youtube without stutter, it loads faster than I can watch. But at school I have max signal bars but loading the same youtube video needs buffer.
It doesn't matter how new or how powerful your phone is if your network's internet is the problem. Different phones don't get different coverage, they are connecting to the same cellphone tower from your network. Network coverage is not phone specific. There's a tower somewhere near your location and all phones in the vicinity of that tower connects to it.