It would generally be as effective as HT and would last for a similar length of time. The advantage is for men who have other medical issues that make taking anti-androgens difficult (fear of needles, mobility, allergic reaction, blood disorders, etc). The downsides are a) it has the same side effects in terms of muscle loss, fatigue, weakness and b) it is irreversible (a major drawback if it is unsuccessful or the side effects are unbearable).
Having said that, we had a member Alex who had orchiectomy when HT failed and did amazingly well for a number of years.