It is interesting that the assumed reason for rejecting a take off generally appears to be an engine failure. In 11 thousand (Perf. A) flights or so I have rejected about half a dozen. Only one was a high speed reject, the rest were at a relatively low speed. But not one was due to an engine failure. I think this is quite typical for most pilots in so much that you rarely stop for an engine failure, it is normally something else.
So diving back in, in a very amateurish way, unless our performance calculations have a "Safety Quotient" against each performance calculation, you can never determine which is the safer. I believe it is far too easy assume that a greater performance margin equal a greater safety margin, but this is too simplistic because it only assumes an engine failure. There is more to it than that. So unless I'm given that information, I'll stick to my company's guidelines and operational preferences.
PM