I love clay pots and used them exclusively for a great number of years.But now they have become quite expensive and I have switched to plastic pots.You have listed the advantages of clay pots, plus I think they are aesthetically more attractive.
I am not sure what you mean by 'slashed' clay pots. I assume you mean pots with a lot of holes in the bottom and the sides, which we refer to here as 'orchid pots' as they are produced specifically for the epiphytic orchids. If that is what you mean these are the clay pots we use here for 90% of our orchids.
As to the problems associated with them - the main problem is when you have to repot. Orchid roots stick to the clay surface and it's almost impossible to pry them loose. Soaking the pot with the plant in it for some time before removing it may save some roots but you are still left with some damaged roots.It is relatively easy with plants in plastic pots as the roots don't stick to them. Another problem is reusing them as old pots retain mineral salts in them due to evaporation over time while the pots were in use.