Okay, you have three basic remote connections out there, and two types of line.
Starting with the line, you have coiled (Which is springy, and without tension, it coils up like a spring) and straight (Which is often much shorter, but is also often covered in steel braid). Both lines are great, both work, there is no worries about one being less strong and more prone to a burst than the other.
If you elect for the straight line, it will be shorter, and easy to cover with a liner. But it will be a bit more limited in how far you can move your marker around and shoot with it comfortably.
If you elect for the coiled line, you can move your marker around from hand to hand, over your head, heck, probably even have a buddy hold it and shoot while you are sitting next to him. But at that length, it can get snagged up on tree limbs much more easily, and if you get a cover for it, it will take a bit to get the whole line in the cover.
For the remote connections, you have a simple QD, a QD with a Slidecheck, and the "new" Pro-Connects.
For a QD, it is a simple Quick Disconnect. On one side, you have the male end, typically screwed into an adapter that you would screw into your ASA, and the other has the female end, typically attached to the end of your hose. You have the ASA adapter on the marker, you screw a tank into the ASA on the hose, connect the two parts of the Quick Disconnect, screw down the on/off on the ASA, and you are shooting. The pro for this is the cost, the con is that if you want to put your marker down, you either have to turn off the air, and shoot the air out of the marker, then disconnect, or you simple take off your pod pack or vest and place the whole thing down.
The QD with a Slidecheck is really the same thing. But there is a tube like thing between the hose and the female connector. That is the slide check. It is an outer barrel that goes over a tube, when pushed all the way forward, towards your female connector, air goes through it with no problems. When you slide the barrel backwards, towards the hose, it does two things: A) stops the air from continuing on to the QD and the rest of your marker, and B) vents out the air from the Slidecheck forward into your marker. It's pro is that you don't have to take off your vest or pod pack to put your marker down, it's con is that it is a bit more pricey.
The last is the Pro-Connect. Really, it's older technology. I have the one that I bought back in the mid 90's. It does everything that the QD with a Slidecheck does, but in one smaller and easier package. It has the male connector that goes to the adapter piece, just like the others, and the female connector goes on the hose. When it is working to supply air, it does not do anything different than the others. But when you want to put your marker down, instead of having to slide the Slidecheck back, vent your air (Which honestly takes maybe half of a second), and then disconnect, these have a button that you push and it disconnects the air supply and vents out the air all at one time. It's pro is that it is slightly faster in connecting and disconnecting, as well as has a few less parts, than a QD with Slidecheck. It's con is that it is pricey.
Hopefully that helps you a bit.