I enjoy both sites and use them about equally.
I don't get the difficulties in signing up for KTM Talk. As to the search, I have good luck with searches over there-even without the Google capability. When the bike categories are narrowed down (RFS, 2 strokes, RC4, etc.) it is a lot easier to focus and find info on your bike.
The KTMTALK classifieds are head and shoulders above the ADVRider Flea Mart, which ranks right there with Craigs list--without the ability to search by location.
Knot headed inmates, overzealous moderators, asleep at the wheel moderators and greedy vendors exist on both sites--call it even.
General "adventure riding" info, ride reports and trip planning--ADVRider wins hands down!
Don't waste your time looking for KTM singles info on ADVRider or looking for KTM Twin info on KTMTalk.
KTMs--300, 518, 990