I currently use the Tough 1 and they fit very well, but the waterproofing doesn't seem to hold up for prolonged periods of rain. Great sheets for keeping clean overnight, but I personally haven't had great luck with them as a long term turnout.
I have friends had friends who have used the Amigo on their larger ponies and have been very happy with them.
If I remember correctly, the Amigo doesn't have leg straps. I personally prefer leg straps for turnouts, especially if it doesn't have a bellyband. I do really like the looks of their neck cover.
My heavy blanket is a Kensington Cascade and I love it. Very well made. Fits great. I normally do not blanket except in the spring after clipping, but it has been so cold up North this year that I have had to blanket one of them full time. The Kensington has been waterproof and has stayed in place. Plus it is quite a bit less expensive than the Amigo. I plan on purchasing some sheets in this same design before Spring.