1080P in NTSC countries usually refer to 24P. It can give you that filmic, stuttery look on fast action and pans. 1080i60 is smoother on fast action, and is almost always used for sports. For web, you always try to shoot progressive where possible.
SD and HD won't match up very well, as SD is of lower resolution than HD. Also, you do not try to mix frame rates.
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