My opinions:
Toynamis aren't worth getting unless you're getting it cheap and even then I'd be careful. I was very disapointed in mind. Too bad I didn't know about Yamatos then.
The Bandais are reasonably costed, very durable and good for banging around but are not as detailed or poseable.
As to the Yamatos. I don't yet own a 1/48, so I can't offer a solid opinion on it. I do have one coming in the mail, though...
The 1/60 Yamato is IMO a fine figure. A lot of the people who don't like them point to the lack of a perfect transformation as a flaw, and while I'd prefer a perfect transformation over a non, I have to say I'd take a well designed figure without it (the Yamato 1/60) vs. a poorly designed figure with it (the Toynami).
I guess it all depends what you're looking for. I'd recommend any of the other three (Bandai, Yamato 1/60 or Yamato 1/48) over the Toynami one no matter what you're looking for...