ShortPixel Adaptive Images vs. Autoptimize's "Optimize images" option

Which one should I use? ShortPixel Adaptive Images (SPAI) or the option "Optimize images on the fly and serve them from Shortpixel's global CDN" on Autoptimize?

Both use the same ShortPixel service, the ShortPixel Adaptive Images API, and both can deliver optimized and "next-gen" images (e.g. WebP), but there are differences.

• ShortPixel Adaptive Images (SPAI) optimizes your images and tries to determine what is the resolution of the image in the browser for the particular device, resulting in better sized images in most cases. For this purpose it has to lazy load the images, which could cause incompatibilities with some plugins and themes (here's how you can troubleshoot that).
• Autoptimize uses a combination of a server and client-based approach: it also optimizes the images by replacing the image URLs with the CDN URL, but client-side logic is only implemented if lazy-loading and/or WebP or AVIF delivery are active.

In simple words, ShortPixel Adaptive Images is like Autoptimize's image optimization, but with a few more useful features and more flexibility. 

Our advice is to try ShortPixel Adaptive Images if you don't have Autoptimize yet, and if you see any incompatibility try installing Autoptimize and use the image optimization service. If you already have Autoptimize, you can start with that, but if you want perfectly sized images for each device being requested, try out Shortpixel Adaptive Images (deactivating image optimization in Autoptimize).