Application opening speed is slower on my iMac compared to MacBook Pro (both M1 8CPU/8GPU)

App launch speed is more often related to storage speed than RAM, GPU, or CPU.

We know third-party cleaning apps can slow storage—I suspect that's the point of John Galt's Activity Monitor comment.

If one computer has third-party utilities (most are useless) that are not on the other, that can make all the difference.

To compare drive access speeds, you can use Black Magic Disk Speed Test or EtreCheck. To also check drive health you can use Drive DX. Any of this may add valuable clues.

The difference may lie in the software they're running. Open Activity Monitor on each Mac and compare the two.

Activity Monitor User Guide for Mac - Apple Support

As I said, "Just a guess". I can't even tell you why there may be a one or two second difference opening an app on the same Mac. Other that the app may have been opened recently and is still cached. Despite having the same CPU they do have other differences obviously.

What i can say is in decades of computer use, I've never timed the speed of an app opening.

Just a guess but it is possible the storage is the difference. If nothing else the SSD in the iMac may be slower.

True. Although I assumed the user had the same software installed on each. Otherwise, the question wouldn't make sense.

I think he needs a third Mac.

😎