There's really only two choices... The small Simrad and the small Raymarine.... I have used the Autohelm 1000 that came with my Catalina 27 when I acquired it in 99.... Othere than me breaking a piece of the case's pin mount... which I fixed with marine tex... it has worked flawlessly.
The deal is, it's only another hundred bucks for the next size up... so most just get the larger one..... If you have 30 footer and you do a lot of motorsailing... then you might want the extra size. But in a lighter, smaller boat.. and you want to use it because you singlehand sail a lot... the smaller unit would perform wonderfully.
It really comes down to spending the extra hundred....