Native SDI-output vs HDMI-SDI adapter for live stream I currently run live streams of amateur sporting events, mainly inside. Currently I am using several Panasonic HS-900ks connected to a PC desktop via RCA cables and several Easycap DC60+s (USB 2.0). As you can imagine, the quality from the Panasonic's gets degraded very quickly. Some of the RCA cables are carrying video over 100ft from source to destination.

I am looking to upgrade the connections to SDI via the Blackmagic Decklink products. That said, I will need cameras that support SDI output, or purchase an HDMI-SDI adapter (~$300). 

My budget is approx. $3000 for a single camera, and since I'll only be outputting the stream at 720p max for the foreseeable future (don't want to overburden end-users bandwidth), I really don't need a fancier camera then that.

Obviously there is a big price difference between a new camera and a HDMI-SDI adapter. Is there a big quality difference, or does HDMI-SDI not really lose much quality? Will it provide the same signal as a new camera such as a Panasonic AG-HPX170 P2HD that provides native SDI-output? I am not looking to output audio from these cameras, just video.
For amateur events, SDI may be overkill compared to using simple Component.  The key for long runs is to separate the various components so that they don't degrade.  There is a similar question here about long distance runs. 

As for HDMI to SDI, there should be no quality loss compared to HDMI as both are digital formats supporting full uncompressed HD streams.  The quality of the converter may make a difference, but there is no technical reason that you couldn't have a flawless conversion between formats.  Both support both YCbCr 4:2:2 and 4:4:4, so the color spaces should be compatible either way.