Any reason to choose a Benchmade over a Spyderco?
Of course...multiple reasons. One can say the same about choosing Spyderco over Benchmade. Whether those reasons mean anything to a given person is subject to one's individual preferences.
As an example, for many years I wouldn't buy a Spyderco knife. Why? I didn't like the hole... not so much as as opening feature as because of how it increases the width of the knife. (Truth be told, I didn't like how it looks, either.)
Some people like Spydercos specifically because of the hole.
For the most part, I have found Benchmade to be more comfortable in hand. Don't get me wrong...most of the Spyderco handles are ergonomically shaped; but the thin flat scales on some of them aren't great for me.
Some don't mind the scales, because the handles themselves are so well shaped; and would argue that Spyderco has some of the best handles around.
I could go on; but you get the point.
Somebody commented that Spydercos were, in general, better slicers. I haven't found that to be the case when compared to Benchmade (some other brands, yes). I have never owned a Benchmade that wasn't a good slicer.
Don't worry so much about brand - find a knife that you like and meets your needs.