What a strange question. And with an even stranger outline.
As far as I know, almost everything produced in the world of pornography today is somehow "HD", though that does not really give any indication regarding how good it might look; it is just above the television resolution NTSC or PAL has.

Assuming you do not only want to shoot material, but sell it as well, going for the highest possible quality you can afford would be my suggestion. It probably does not hurt to buy, rent or - well - download video material for comparison of, say, Digital Playground and Vouyer Media with Anabolic and Zero Tolerance productions. The former look really good, while the latter mostly lack fine details; due to cameras, lighting and post-processing - though of the companies mentioned only Digital Playground seem to utilize the last aspect to any extent.

By the way, an anamorphic widescreen DVD "fills the screen" of widescreen television sets quite nicely; almost all productions still look framed all right when zoomed in to fit on a 4:3 set.

Depending on where you are based, companies renting cameras and equipment might be able to help you to find an affordable solution.

Good performers in a solidly-crafted production could be an advantage in what seems to be a very competitive industry.