1080i vs. 1080p for gaming?

1080p is better for everything except price, unless your TV is very low quality you wont notice the difference too much. I wouldn't recommend wasting money to replace it with a 1080p television unless your 1080i one is broken. Pretty much 1080p allows for a smoother image as it paints the screen in one pass, 1080i paints every other line and so it takes two passes for it to paint the image onto the screen. The sequential paint happens in 1/30th of a second so you aren't going to notice unless you sit it next to a 1080p screen.