Part of the issue of stronger comes down to what breaks spokes in the first place. Do spokes break in normal touring usage because they weren't butted or straight? I don't think so, except at the extreme margin. Spokes break because of three main reasons:
1) improper instalation, this means a slight bias against any machine made wheels that require certain less than totaly optimum materials and techniques in building, or it means bad hand building. As to the latter there are presently at least 3 specilist books on this subject. People still argue about Jobst's book, and the other two recent ones have been warmly received by insider reviewers with quotes that imply something precious has been revealed. Apparently it isn't all as obvious as it might be. Further evidence is the lords of spokecraft, people like Jalon Hawk, Peter White, and quite a few others, who have a reputation for doing it right which is only possible if someone is doing it wrong.
2) Bad materials. A lot of wheels are not being built out of DT Swiss anything. Is your Chinese butted spoke machine made wheel going to outperform the super wheel built with DT straight spokes, DT hubs etc...
3) Bad fit in components. Good materials poor combos. It's not just a mater of what you use and how you use it, but there are spokes that will not be properly supported when used in particular hubs. There has been some complaint about certain spokes being redesigned for insertion in the machine sequence that no longer hold up to custom wheel standards.
Do properly built wheels break? I don't think they do. Why do my wheels never break at my 220, while someone weighing 100 pounds has lots of trouble. Why does Jobst recoment not replacing spokes when rebuilding wheels due to rim failure? The focus needs to be on what maters, and part of what maters is that straight spokes are more rugged outside of the tensile plane in which spokes snap when they are riden on. Neither butted nor straight spokes should break in use, so you need to look at other sources of breakage like panier hooks in the wheel.