First of all the difference between 1080p and 1080i is imperceptible to the human eye. Both are 1920 x 1080 pixels. The ” p” stands for progressive” scan and the “i” interlaced scan. Both will record the same and display the same.
Now that we got that out of the way, 720p is HD but a lower resolution at 1280 x 720 pixels. Most surgical microscope cameras are now 1080p/i. The newer cameras are that beginning to become available are the “4K” or 3820 x 2160 pixels. However, if you do not have a 4K recorder or 4K monitor, it will not benefit you. If you plan to upgrade your recorder and/or monitor to 4K in the future, make the investment now.
4K (2160) cameras will be more expensive the 2K (1080) cameras, however they will display more anatomical definition due to double the amount of pixels.