I’ve a tried out a few of these for grocery shopping. I had some thoughts, as far as I can remember very much in line with
@Kitty suggested considerations
The wheels need to be larger and bounce. So as to perform better on the roll and reduce pain from constant vibrations.
Most wheels are quite rubbish quality. Too small. Hard or overly soft. The foam type ones are better than the hard plastic but still not great for vibrations. Rubber is optimal for shock absorption. This consideration applies even where not putting weight on the device. Vibrations travel up your arm from even a very light hold. It’s tiring and uncomfortable.
Although I am not tall I still found that it was hard to get the appropriate height for push bars. These are usually set a bit lower. As people are expected use the bars to transfer weight off of their feet so may be leaning down on the handles. If you’re not doing that, you’ll want it set higher as did I. These bars are adjustable, but most commonly by increment only and these points may not be very close together, making it difficult to hit a really comfortable hight.
I used these devices to lightly balance and to carry stuff. I found elbow high with me standing up straight to be the right height. I rested hands or wrists or forearm on top so I could vary my hold to make it more comfortable pushing over bumps on hard ground.
Also I don’t think I have a wide stride but I constantly bashed my knees and feet into the basket on one and seat on another. Maybe because they’re not designed to walk fully up right with or maybe because stuff for disabled people usually not that well designed.
If you don’t need a roller for stability of a specific variety,
I’d say the three wheelers can be alot better than the fours, there seems more space to accommodate a fully standing person with an average stride. And they’re more easily manoeuvred up and down curbs.
But you do have to find a good seat also and there are more models to choose from in the four wheeler variety as far as I could see. The seat must have a comfortable back rest that hits not too low and not too high so that it provides some decent lower back support. That’s not something I could find so I didn’t use mine for sitting.
The seat would need to be at a height where your thighs are pretty much horizontal with feet flat on the floor to be any kind of substitute for a bench or a chair and provide any real support or muscle relief. But mostly the seats are much higher and more like the experience of propping your bum on the edge of a wall. The reason for this is that a lower seat would get in the way of actually being able to walk without bumping into it. Because unfortunately disability equipment makers haven’t looked at all the billions of buggies for children which somehow manage to overcome this problem just fine. So anyway some better models have an adjustable seats so you can leave it high for a brief uncomfortable perch and push it down for a, relatively, enjoyable rest. Or flip up seats, more common on the three wheelers maybe.
Oh I forgot to say earlier….
If you’re of lower or average weight consider opting for an aluminium version over a steel one for the weigh savings. Because you’ll be lifting it probably more often than you anticipate and even for a few seconds it all adds up. I bought all mine secondhand and there are many more steel ones around as cheaper to produce. If I were in the market for a new one I’d probably choose an aluminium version.
Two more things I forgot to add…
The breaks need to be in a good position for you to easily hold or reach them and function smoothly. Good luck with that one. Also these things have break wires all over the place. Manufacturers could tuck them away but they don’t. Because you know.
For anyone on the heavier side who wants or needs to lean on the device properly for leg support suspension is an available option. I don’t know how good it would be. For anyone on the lighter or middling side I was told it’s not available. But that may have changed since I last looked.
Conclusion.
I would recommend looking at quite a few online pictures and videos and wherever you might find them the invaluable resource of explainers or reviews by experienced disabled people. If you can try some out in a mobility store even better.