Should "universal pedals" be avoided? Are universal pedal axles weaker than standard axles? If so, should they be avoided?  

These are inexpensive pedals so let's focus on inexpensive normal, solid axles vs these universal pedals.



Each pedal comes with a 1/2 inch and a 9/16 inch adapter that must be screwed into the pedal body.

The left pedal adapter threads in with a left hand thread, the right pedal adapter threads in with a right hand thread.



Edit 4/10/2020  

Would they be strong enough for any of the following applications?  

Could these pedals be strong enough for some applications not displayed below? 

The following bikes were chosen because they come from bike shops with roughly comparable inexpensive plastic pedals.  

All the bikes are Trek because it was easy to find a wide variety of Trek bicycles. This is not meant as an endorsement of Trek.

Option 1: Trek Tag Along


Option 2: Trek cruiser


Option 3: Trek children's bike


Option 4: Trek 24 inch wheel bike
In context of the low cost pedals, you need to look at the user and how they ride. Would I trust them on a trials bike or downhill MTB?, no, but then I would not trust a cheap pedals with a one piece axle.  Would I trust them in a situation I would trust a similar pair of cheap one piece axles, absolutely.  

In theory the two piece axle will be less reliable as it has another failure mode that does not exist on a one piece axle. However, the failure of the extra threaded join is probably much less likely than the pedal to crank join, due the thread locker. Therefore, the increased risk is marginal. 

So the question is not 'should they be avoided because they have a two piece axle", its "Should cheap pedals be avoided"