you mean old cx550
i have hdr xr550....similar to cx550
cmos sensor of cx580 is 1x 1/3.91" CMOS Sensor... while cx550 has 1/2.8-inch CMOS sensor...
i have the sony hdr xr550...and it is consider a hi-end semi pro camcorder
while the cx580 is considered midrange camcorder...the newer poket type sony hdr gw77 (avail next week) which i am going to get have same specs as cx580...and can bring anywhere and pocketable.... http://www.camcorderinfo.com/News/Sony-Adds-Waterproof-HDR-GW77-to-Handycam-Lineup.htm
I had the xr550 too...unfortunately broke :-(
But , though the sensor on the old sony xr550 is bigger then the sensor of the cx580, possible that there is NONE of the NEW add on features of the cx580 that are BETTER then the old XR550 ? I mean, yes, sensor dimension is important, but other features too... ie... 60p and/or IS ecc.....
What do u think ?
As far as the new camera u said, for me the lack or lens tread and the small internal memory dimension is a no, no :-(