Fillings are less destructive to the tooth. The issue though is how strong is the tooth structure. If the tooth is weak, then getting a filling instead of a crown might make the tooth vulnerable to cracking. There is an option that is between a filling and a crown, which is an inlay or onlay. An inlay or onlay is custom made in the lab to fit the tooth. An inlay or onlay will strengthen the tooth, while a filling makes the tooth weaker. A composite filling is not a good choice for a large cavity in rear teeth. An inlay or onlay would be a much better choice. I have a combination of composite fillings, inlays and onlays, and crowns. Most are inlays and onlays. The composites are smaller fillings, especially those not on chewing surfaces. My main objection to crowns was the metal backing and metal post. Only one of my crowns is like that. The rest are all porcelain.