These side loader cages are a must if you have a small bike with a tight front triangle. They make it easy to insert and remove bottles, and I've never ejected a bottle riding over gravel or rough pavement. These certainly aren't cheap, but are durable and last many years with no degradation in performance.
I got these for my gravel bike so I can use a frame bag but I'm not completely sold that they will be secure enough on bumpy descents. I'm going to try wrapping part of it with a tacky tape, but I would've expected these to have a tighter fit. If you're just riding on smooth roads they're probably ok.
I have these on my road and mountain bike. The side load makes for easy removal and insertion of my water bottles. I use 24oz bottles and have never had one bounce out of the cage. I have tried a couple other brands but they did not perform the same. I have been using them on my road bike for about five years and my mountain bike for about a month. I have ridden over cattle guards and some very rocky terrain with no issues.
Got the bottle cage and really like the ease of use. Have to say the ordering process, i.e. determining which one to order is a little confusing as to which side of the cage you prefer to use.