What is the Full HD?
Full HD Meaning 1920x1080/50p. Actually Full HD is 50p not 50i. But,Videographers mostly use 1920x1080/50i Recording mode. First understand what is i ,and p. i mean interlaced mode. p mean progressive mode. What different between I and P?.

Interlaced Video
Interlaced video takes two source frames of a lower resolution and weaves them together in a way that creates a single high-definition frame. By taking video that occurs a fraction (60th) of a second after the first, the appearance of jagged lines and various other video phenomenon can be reduced considerably. In short, a 1080i video is comprised of video that includes 540 horizontal lines shot 50 times per second, with occurrence capturing either the even or odd set of horizontal lines out of a larger 1080 lined image. Every other frame is interlaced with the one before it, turning the 50 frames of 540-line video into a single 1920×1080 image that changes 25 times per second. Interlaced video jerk occurs during fast-motion sequences as well as moire or strobing artifacts that sometimes appear when striped shirts, plaid jackets, bricks in a building, or similar types of objects are shown.

Progressive Video
Progressive video Displaying whole frames as single images. Progressive video contains more data than interlaced video and as a result images displayed appear sharper and more detailed, with no motion artifacts visible when watching sport or other quick motion sequences.

Which is Better Interlace or progressive ?
Blu-ray player, LCD & LED Televisions and monitor are support (1080/50P & 720/50P) only. Most camera companies Produce only 1080/50i and 720/50p. Meantime, editing software's also not support 1080/50p H.264 blu-ray conversion.

The advantage of having a larger physical image with slightly more detail than you would find with 720p should be taken into account. You’ll get a larger, sharper image with 1080i than you will with 720p, but motion lines and other interlacing artifacts can certainly cause a disappointing overall viewing experience.

The video quality of a 720p video is sufficient for most cases, and a lot of people will have a hard time telling the difference between the two.