This is always something I feel is going to be a hard choice for me every year, and then it's not. I like both the white and black screens, and both have benefits and disadvantages.
IMHO:
The black screen blends videos and some apps better, as well as "looking the part" for a stealth-y style. I even find that the earpiece, camera, and sensor is more inconspicuous on black screen iPhones. But at the same time, the black screen tends to smudge more, show more marks, and get generally greasy/dirty easier.
The white screen iPhone plays well with most of Apple's built in apps (email, messages, maps, etc.), looks better with most cases, hides smudges better, and generally "pops" more (much more vibrant). A problem is that video and media are much less blended. Earpiece and cameras also show much more obviously with a white front.
I'm THAT type of iPhone owner who usually goes with the most recent color, which is why the front screen color has almost never been a "make or break" with me.
iPhone (original): black screen/sliver back (only option)
iPhone 3G: black screen/black back
iPhone 4: black screen/black back
iPhone 4: white sceeen/white back
iPhone 4S: black screen/black back
iPhone 5s: white screen/gold back (favorite design ever)
iPhone 6: white screen/gold back
iPhone 6s: white screen/rose gold back
iPhone 7: black screen/jet black
I skipped the white backed 3G because it thought it would clash with the black screen.
I got a my first iPhone 4 in black because (we all remember this debacle) the white iPhone 4 wasn't released until April 2011. I got my second iPhone 4 once it was finally released in white, months later. I wanted the white one from the beginning because it was SO different to my 12 year old self.
I then got my iPhone 4S in any configuration that was available launch day, which happened to be a 16GB black model (had to get my hands on Siri).
I had to get my iPhone 5s in Gold. It was so "new" and "different". I feel that this was the best iPhone design ever. It's so precise and straight up gorgeous. It felt like a jewl when I held it.
I kept the Gold with my iPhone 6 because silver was too basic for my taste, and the Space Grey never did anything for me. It just felt like another shade of silver, with a black screen.
I got my iPhone 6s in Rose Gold because it was the "new" color.
When the 7 came out, I was already preparing to get it in Rose Gold again, but then I saw the jet black-- and I was dead set on it. Jet Black would be my next color. Both types of black were so damn good looking. I just finally got it this week after I preordered it on 9/9. This is my second or third favorite designs. It resolves all the problems I had with the 6/6s design (revised [on the Jet Black practically invisible] antenna lines), less clunky looking camera bulge, water resistant, etc.
I will admit I lean toward the white screen phones ever since the 4, but the 7 swung me back.