The Harris is a great bipod if you want something cheap and it has some advantage to speed in deploying the spring-loaded legs. However they tend not to be as durable, need aftermarket support to get with the times (QD, arca, podlock, spike feet). The Atlas seems to be far more durable at matches. It you see a bipod break at a batch it tends to be a Harris but then again it is cheap for a reason.
With enough money in add-ons you can get a Harris to have quick release, better locking, and better feet.
Also the Harris is not very accurate in the shortest length as the leg length is spring-loaded and in the shortest position the legs have a lot of spong.
In PRS many still use the Harris but far more that started with a Harris have switched away to an Atlas or other model with similar features. The Harris is not nearly as useful in alternative type positions as is does not have the flexibility of the leg design found in an Atlas (and not other brands). The leg design of the Atlas provide 3 different range of heights with the stock legs and the legs can be loaded in any position, unlike a Harris.
When it boils down to it, you won't go wrong with a Harris but you will be able to do more with an Altas. Just depends upon what you plan to do with it. Most people don't need good equipment for the occasional range day or yearly deer stand hunt. If you use your gear in harder conditions or learn to use more alternative shooting techniques, an Atlas will be a better choice.