I have a Sherwood Amphos Air that I've been very happy with. And, the Sherwood Widsom 3 is a pretty solid, very reliable unit.
Knowing what I know now, if I were purchasing a new computer, it would definitely be the Shearwater Perdix AI. When I bought my Amphos Air, I didn't want something really big hanging on my arm. While I liked the Shearwater Petrel, the size caused me to shy away from it. Having not seen a Perdix unit at that time, I was under the mistaken impression that is was similar in size to the Petrel. Additionally, most LCD screen computers were/are difficult to read on the surface. After actually seeing a Perdix, I'm sold. It's not nearly as big as a Petrel and a lot easier to read on the surface than most computers with similar style screens.
I like the Perdix AI so much that, when I can afford it, I'm going to buy one and retire my Amphos Air to a backup role. The good news is that the Amphos Air transmitter is compatible with the Perdix AI. And, as many have already pointed out, it's the last computer you'll ever need.
Hope this helps.