The integrand is highly peaked.  It is approximately an impulse function where much of the mass is concentrated at a very small interval.  Plot the function and see for yourself.  This is the likely cause of the problem.

Other types of integrands where you could experience problems are: integrands with singularity at either limit and slowly decaying oscillatory integrands.  As to why integrate performs better than adaptIntegrate in this situation, I don't know.  You have to study the two implementations.   Wynn's epsilon algorithm is an extrapolation method for improving the convergence of a sequence.  This could be an explanation for the better performance, but I cannot say for sure.

Hope this is helpful,
Ravi
-------------------------------------------------------
Ravi Varadhan, Ph.D.
Assistant Professor,
Division of Geriatric Medicine and Gerontology School of Medicine Johns Hopkins University

Ph. (410) 502-2619
email: rvaradhan@jhmi.edu<mailto:rvaradhan@jhmi.edu>


	[[alternative HTML version deleted]]

