Can't say I have seen anyone comment with first hand knowledge of these kayaks.
I've seen the SEAK at Anaconda - looks like a good beginners yak, and the price is certainly very attractive for an entry level kayak. Moulding quality wasnt outstanding, but looked ok (maybe just give them a good look over before you take one home to make sure you get a good one)
The Invader I have never seen before, but it looks like it would be the most capable in rougher conditions. I'm no hull design engineer, but what little I do know about kayak hull design - its on the narrower side for a fishing kayak at 70cm wide so may be a bit tippier than the other models mentioned, and the hull shape looks very rounded (lacking any defined chines) so I don't know if it would have as much in the way of secondary stability. So in short, could be a bit easier to accidently flip this yak than the other kayaks - but should be a faster boat