Archer
Peep sights with the alignment rubber have a tendency to ware and brake and they will usually brake at the most inopportune time. If you have a good archery shop or have the knowledge I would go with a "no twist" type of string such as Barracuda which will not twist during the draw and have a your peep into that string. If set up right it will always be aligned at full draw and you will not be constantly changing rubber. Front pins are centered in your rear aperture. the guard on the front pins are for protection of the pins and I would not use it for sighting purposes. Sighting is like sighting a peep on a rifle.

Kush Slayer
i dont know which is better but you just look through the hole and put the dot from the sight on the target, no lining up necessary

dumdum
They are basically the same but I like the top one the best. You do not need a guard to use the peep. A few years ago when you shot a peep you just centered the pin in the center of the peep. But if it is for target shooting the smallest aperture you can get would make you more accurate. But if it is for hunting you need a medium to large aperture in the pin. The reason for this is that under low light conditions it is almost impossible to see your pin through the peep if it is too small a hole in it. When you install the peep, you need to adjust it to the point when you pull back and get ready to shoot the pin is centered in the peep and you do not need to contort your head in different positions to line it up. When you move your head to make the sights line up, it is destroying your shooting form causing you to miss.The best way to adjust it is keep tweaking on it until you can draw your bow back with your eyes closed and when you open them the pin is in the center of the peep. Good luck!