Only consideration that needs to be made is....on small flies like say # 20 and smaller..maybe #18's as well, the down eye takes up some of the hook "GAPE", or gap, and you might not hook a fish as securely. I might make a case that a straight eyed hook is easier to tie in that I can see the head area better, and not crowd the eye because it is under somewhat. You might also like to thread the tippet through a straight eye believing it is easier to do than a down eye. I've had trouble threading a leader through a down eye, and turn the fly upside down, and the tippet goes right through. You probably have good eye sight, and not a problem. I never see a straight eyed hook for flies fished subsurface..all are down eyed.

Where are you going to be fishing? I have a serious lack of midges to fish with, so I'm in the same boat. Especially since the trout I was fishing for came from a spring creek, I needed to have midges for sure.