The smaller one doesn't give azimuth info, which is IMHO as much use as a chocolate teapot
I can understand why you would say that, but I dont agree. Have you tried it?
You will get an alert at five miles, and a seperation level. A thousand feet above or below and its not a threat. However, if it is at the same level keep out an even more careful eye. If the traffic is a significant threat the distance will close - at MOST GA speeds, even head on, not too quickly. Within one mile, you will get an urgent alert - my that concentrates the mind, particularly when, as is quite frequently the case, you STILL have not spotted the traffic. You may well have elected before to have built in some vertical seperation. In fact in some ways the azimuth information can be a distraction. Without azimuth you fall back on a 180 scan, never forgetting that something else might be closing from the other azimuth that is not transponding.
All I can add is that I have used the "system" for hundreds of hours. I have not yet had an urgent alert without eventually seeing the traffic and my vertical seperation has always ensured there wasnt a risk of collision. I know there is an inherant risk that TAS in any form is not completely accuraye in either veritcal or horizontal reporting but I feel a great deal happier with it than without it.
If you havent tried it, it is well worth a go, you have very little to loose with the cheap as chips unit and perhaps something to gain.
It is worth a thought that it almost certainly will never happen to you, but it has only got to happen once. In a few thousand hours I have had three that were close and one way way to close for comfort.