I give it 50/50 at this point who delivers first between TH and KNC. I think both are likely legit.
Terrahash isn't developing their own miner though, they're just providing boards and case+PSU combos for Avalon chips. If they deliver later than KnC for any other reason than BitSyncom not delivering the chips on time, that's a huge failure on their part; not that I expect them to be slower, since, again, they're just putting chips on boards.