The trouble is that very very few people make good managers. So few that trying to work out whether engineers make better or worse managers is a bit difficult.
This is made worse by the fact that many good engineers fight shy of becoming managers, possibly because they have so little respect for them and possibly because many engineers are far happier engineering than managing.
It might well be that if engineers had no choice and were forced to be managers they might, as a class, prove to be better than others.
Sadly, there is no evidence for this either.
Perhaps I should say, I have only personal experience to go buy here.
In fact while I know of only two or three people (in nearly 35 years) who were good managers they lasted only a short time (less that 3 years in total) before moving onwards and upwards or out sideways.
None of them were engineers.
On the other hand, some of the bad managers were engineers. One problem I noted then was that they tended to give full rein to there engineering instincts and very little weight to other factors.
In most companies there is an Engineering department and a Sales and Marketing department.
In one company they tried the experiment of an Engineering and Marketing department.
They created a number of great products that no one bought.
And that's something I have witnessed several times before.
JMW