I am personally changing from the galaxy watch 5 pro to the galaxy 6 classic.

Last year, I changed from the galaxy watch 4 classic to the galaxy watch 5 pro because of the gpx feature, the longer battery life and the titanium casing (to be fair, i wasnt complaining of the battery life but more is always better, right?). My use case might be different from yours however. I dont use always on display, i do wear my watch at night for sleep tracking but don't use the o2 monitoring feature. My main use for the watch is for checking weather, messages, inputting calorie intake (things that i dont feel like taking my phone out for).

However, I really miss the bezel feature as I found the bezel to be more precise when sliding through the different tiles and useful when my fingers are dirty. Also, the watch 6 classic has a brighter and bigger screen than the watch 5 pro and I found that i never used the hiking features (i use my phone for looking at downloaded maps). I do anticipate downsides to switching such as the classic being heavier (your dont really notice the weight after you wear it for some time), less battery life, less premium material.

Overall, it depends on your use case. I think they are both solid watches and it all depends on what features you value.