They are not as fast as an SSD.

In some use cases they are, since they contain an SSD as a large cache. They are also a lot cheaper than an SSD, so it's nice to get some of the benefits without all the cost.

For me solid state > moving parts. Faster and run cooler.

Edit: afaik the only moving part in the Surface Studio are the fans. Replacing a fan is an annoyance but at least it won't lead to data loss!