It is one of those things that you can go with family tradition, or want to shake things up a bit, or you may decide to do it based on if things are running early or if your timeline has had to be pushed back. Luckily this is one of those things that won’t be ruined if it doesn’t happen at the exact time you were planning. (This is where flexible wedding pros come in handy)
Some say right before the dinner. This is good if everyone is at the reception site and have had time to enjoy cocktails and dinner is not quite ready yet. However if it takes a bit longer to do the pictures than planned you may want to consider doing it after the meal, or after the head table is done eating. At this point all the guests should be through the buffet line, or everyone should be served. And you still have a pretty captive audience.
If you are having a plated meal, you could always do it between salad and the main course. We would want to make sure that works with the timing of the main course so you get the best flavor and texture that the chef has timed out to make it perfect.
One thing you want to keep in mind is not put it off too long. People start wondering off and getting into their conversations. Another reason is you don’t want to get too much liquid curate in your people doing speeches.
Remember to trust your wedding pros. That’s why you hired them in the first place. They have done enough to know what works and what doesn’t.