The remote coil is a nice accessory to have because the sim15 is a heavy gun. Running the coil will drastically reduce the weight of the gun, but it of course has its drawbacks. The main problem that I have run into is the coil getting tangled in it self, this makes it alot more difficult to use the gun and while running around dodging paint the last thing that you want to worry about is untangleing the coil, which can sometimes be difficult.
If you buy a sim4 or 15 with a magazine kit, you are going to need to get a remote coil. I dont know how many other brands will work with the ariakon, so I would play it safe and stick with ariakon.
Overall I like running with the remote coil because it makes it easier to run around and play by reducing the weight on the gun and removing the tank which can be a big obstruction.
Just a quick note: All brands of remote lines will work with the SIM series air-through magazines (clips), so long as you have a quick disconnect on the remote line, to match the quick-disconnect nub on the magazine.