WP 34S integration accuracy

[lrdheat]

I integrated e^(3x) * sin(4x) in fix 4 mode and got an instant result accurate to 3 significant digits. This surprised me as I expected at least 4 digit accuracy. Then I had the vague recollection that for some problems where the area under the curve is quite small, the use of scientific notation would provide greater accuracy. Sure enough, in SCI 4, I get 9 significant digit accuracy.

I'm wondering...is there a rule of thumb to go by as to how to choose the best entry mode for an integration?

Is there a nice overlap between the 2 entry modes where one can depend on high accuracy, or is there a gray area where neither entry method would yield outstanding (subjective, of course) accuracy? (It's clear to me that if such a gray area exists, the achievable accuracy would still be accurate to more digits than then the displayed result)