When used in conjunction with a plate carrier it will save you money because you have a dual purpose item. unclip it from the carrier & snap a harness (or compatible bag) and you're in business. most harnesses are easy enough to throw in a bag or dangle pouch, so if you need to drop weight in a crap scenario you can shed your carrier while maintaining the ability to fight.
If you're up where it gets cold you can wear your carrier on the inside of your racket & throw the chest rig on the out side.
Doing some light patrols or recon? go with a chest rig. The spiritus M4 is an example of a highly customizable micro chest rig. minimum is can carry 3 rifle mags, but you could opt to carry 10 on that sucker (I'll leave some links).
In my opinion, save that $40-90 your going to spend on mag pouches or shingle for your carrier, & go with a chest rig.
look at shop all to see the accessories,
a clone if the MK4 can be found here;
(scroll down to see basic set & premium set)
here's a vid of what it looks like.
And there ya have it.