I once lost a friend over this argument, but I think divorce is worse, especially after a very long marriage. Just think about it, if you're over 50 (like me) and have been married your entire life and he kicks the bucket, everyone gathers around you, you're the poor grieving widow, you have a funeral, a good spread afterwards and lots of sympathy from friends and relatives.
There is a support system for widows, there are rituals in place to help them grieve. You can’t sit shiva when you get divorced, no one brings casseroles, there are no sympathy cards. In fact friends may shun you as though divorce was catching. Or you may be blamed for driving him away. Real sympathy and understanding is in short supply. It may take longer to recover from a divorce than from the death of a spouse.
In fact I’ve been told by a girlfriend who went through both that her first husband dying was easier than her nasty divorce. It's harder to mourn someone who not only isn't dearly departed, but may still be around trying to make your life miserable. Then there are all the friends who constantly tell you to move on already. At least if your husband dies you get a decent period of mourning. You're not expected to move on as if the marriage never happened. When your husband dies you get to remember him with affection and think about your long, hopefully mostly happy marriage. When you get divorced after let's say twenty-five years, you have to try to forget your long, probably mostly unhappy marriage. It's like losing a huge chunk of your life.
Did you ever see Eternal Sunshine of the Spotless Mind? I cried for twenty four hours after seeing that movie. It's about a couple who break up and the woman, played by Kate Winslet, undergoes some futuristic procedure to erase her memory of the relationship. Then her boyfriend, played by Jim Carrey, undergoes the same thing but as his mind is being erased he starts fighting the process because he doesn't want to lose all the good memories as well as the bad. That really got me. I realized that because my marriage ended badly I'd lost eighteen years of my life, good memories as well as bad. If my husband had died I would have gotten to keep those good memories. That just devastated me.