Performance difference between default semantic model and custom (new) semantic model?

I believe I managed to query the default semantic model in cold state now.
First, I updated (replaced) the data in all the Lakehouse tables included in the semantic model, this should set the temperature of all columns to zero.
I also let the semantic model stay unused overnight, for good measure.

Then I refreshed the visual in my report. Now I got a DAX query duration of 4819 ms for the default semantic model. This is quite similar to the durations I got for the cold state custom semantic model yesterday. 

However, I also tried refreshing the visual in the report which is connected to the custom semantic model. Then, at first attempt, I got a DAX query time of 9100 ms (new all-time-high!). Yesterday, I had disabled the auto-refresh on the custom semantic model. So it had stayed unused, and not refreshed, for approx. 10 hours. Still, I'm surprised that the Performance Analyzer showed a DAX query duration which is around 100% longer than yesterday. 

I then manually refreshed the custom semantic model in Power BI service (Fabric workspace). Then I refreshed the visual again, and the DAX query time was now 6890 ms. Still around 50% longer than the measurements I got yesterday.  

Then, I repeated this procedure (refresh the custom semantic model, then refresh the visual) several times. During these runs, the durations I got was similar to the durations I got yesterday.
Maybe the Fabric capacity just needed to "warm up" before it was able to produce similar DAX query durations like yesterday?

I guess my key findings at this point are:

• Updating data in a single table in the semantic model, seems to only evict the columns from that table from cache (column temperature gets zero). Columns from other tables in the semantic table, still have high temperature. This is great for the end-user experience, as high column temperatures means visuals render more quickly 😀
  
  
• I prefer the custom semantic model over the default semantic model, because
  • it allows server timings in DAX studio
  • it allows column temperatures to be reviewed by using DMVs
  • it allows manual refresh (and scheduled refresh)
  • the modeling experience of the custom semantic model is found inside the semantic model item itself (which is intuitive)
    
    
• I disfavor the default semantic model, because
  • it seems to have limited functionalities compared to the custom semantic model
  • the modeling experience of the default semantic model is unintuitively placed in the SQL analytics endpoint, and not in the semantic model item itself
  • I want to remove the default semantic model from the workspace, but I don't think it's possible
  • I don't understand the purpose of the default semantic model
    
    
• It's difficult to compare the cold state performance of the default semantic model vs. the custom semantic model, because I cannot manually refresh the default semantic model.

Any corrections or additions are greatly appreciated 😀