I've literally tried dozens of different sight combinations over the years. Because rear sights typically come in fewer height options than the front, order the rear you want and shoot some groups to determine how much higher or lower you want your front sight to be from factory to achieve your desired POA. Personally, I prefer around a 1.5" 6:00 hold at 25 yards.
I would highly recommend Dawson Precision's tritium charger rear sight. It comes in two different notch widths (.125, .145) depending on your front sight width and preferred sight picture. The rear of the sight has 2 very small tritium inserts for use in low/no light. The edges are nice and rounded for no-snag when drawing from concealment, but the front of the sight is undercut slightly, with large serrations that can very easily grab clothing for one handed charging or malfunction clearance. Just run the slide down your jeans and the slide will grab and cycle - no trying to catch the edge on a holster or belt, etc.
https://www.dawsonprecision.com/Product ... 1388518387No pics of the one for the Shield, here's pics for the Sig to get a better idea what they look like:
https://www.dawsonprecision.com/Categor ... ear+SightsThe idea is that in low/no light with both eyes open you want to be able to tell the difference between the rear and front sights easily. The smaller rear vials really help with this. You really need your front and rear tritium to be either different colors, or different sizes to differentiate them. Otherwise you just end up with a bunch of dots in darkness and you have to move the gun around to determine which dots are which. The larger front sight vial also draws the eye to it more so than the smaller vials, so aiming with this combination is much more instinctive to perform, even with both eyes open in total darkness when you have 6 dots in front of your eyes your mind needs to figure out rapidly.
After installing the rear, shoot some groups with your factory front, and measure the center of your groups from POA, and use the formula on the following page to determine the proper front sight height to match with your rear:
https://www.dawsonprecision.com/Categor ... GHTS+FRONTThen simply find someone who makes a front sight in that height, and put it on the gun. It takes more time this way, but by ordering them separately your guaranteed a prefect sight picture. I'd obviously go with a tritium front with a normal sized vial. Here is what I'd recommend - nothing too fancy:
https://www.dawsonprecision.com/Product ... 1388518383They only list 4 heights for the shield, but what's nice is you can call them and they'll make a custom height front sight for you if that's what you need. They show a lot of stuff out of stock right now, but last time I ordered sights from them what I ordered was also listed as out of stock, but it arrived in just over a week.
Any properly height and width matched tritium front sight will work, but I still very highly recommend the charger tritium rear sight. I have them on all my carry guns.
$0.02