Avoid ionizers. They do help prevent algae, but they do not sanitize and they risk expensive and unsightly stains.
A SWG can sometimes be an issue for natural stone work. It is totally fine with just about anything else. Having problems is actually quite unusual, even with natural stone, but when you do have problems they can get expensive.
He claimed corrosiveness on plaster and natural rock coping over time.
I worked with a guy last week who has had a SWG pool for 12 years in Tucson and has had no problems, still using the original Hayward pump.
I will see what PB #2 says next.