I've tried several designs of sub-irrigation including variations with auto valves, with soil, soil-less, and coco. I am for now back to coco, but with automatic top irrigation. If it works as well as it did with my first solo run, I will likely stick with coco and top irrigation for my indoor canna grow.
The problem with soil for me is that if (or in my case it seems when) something goes sideways it is near impossible to do anything smart about it because there is no way of knowing what is still left in the soil mix that will screw with nute balance. To add to that issue, I have always had problems late in sub-irrigation with salt nutes due apparently to salt buildup. Water-only grows sort this issue, but add the nute balance issue with soil. Sigh. For now it is back to coco where shit can be corrected, and top irrigation, which avoids salt buildup. Pretty much boils down to better control of a grow. Different strokes eh?