It depends on what works for you. Yes, that is really the best answer.
Actually, this is the best answer so far. I couldn't deal with cheese sandwiches, but they work for at least one person.
The best energy bar at 40-60 miles might be a gel. You body absorbs them more easily. The downside is that there are about 90-120 calories in a gel, as compared to about 240-300+ in a bar. You need to wash either of them down with water.
I find gels easier to deal with as the ride gets longer, but that's me.