Vests vs. Harnesses
Harnesses are belts, frequently with loops that suspend the belt from a shoulder harness, to keep heavy paint pods from pulling the belt down. Most harnesses are essentially bare bones, they have space for pods, and often for a tank, and that's it.
Vests are a more robust version of a harness. They still usually have support at the shoulder, but they cover the chest and back, too. Vests can be particularly useful in scenario games where you might be carrying around radios, maps, or other similar gear that needs to be stored someplace. Vests also provide some small degree of protection from shots, because even when they're made from thin materials there's another layer of fabric between you and the shot.
Types of Vests & Harnesses
There are two basic types of vests. The first has built-in pockets and pouches, designed to give the average player enough places to store their gear to be satisfied. The other is designed to evolve based on the needs of a certain game or scenario, and is often called MOLLE, which stands for Modular Lightweight Load-carrying Equipment. MOLLE is just one of many different modular systems, collectively called PALS (for Pouch Attachment Ladder System). Because it is the standard used by the US military since 1997, it is the most ubiquitous PAL system, which means it's easier to find compatible pouches, and is essential for anyone looking for a true MilSim feel.
But what is a pouch and ladder system? It interweaves straps built into a vest or harness with straps attached to a wide variety of pouches and pockets. This gives you a huge degree of freedom to customize your vest exactly to your specifications. Is that magazine pouch a little too high or far left? On a standard vest, you're stuck. On a PALS, you just move it. Decide that you need one more pod to fit your playstyle? You can do that with PALS. Want a sidearm holster? Or a pouch to dump spent pods? Pouch and ladder systems are incredibly versatile, and many large pouches come with even more netting, so you can even put pouches on pouches.
The major downside to a modular harness is the expense. These vests can cost as much as a standard one that comes with pockets and pouches, and with the modular vest you usually have to buy these separately. While most modular add-ons are relatively cheap, those prices can add up. Choosing which vest is right for you comes down to how much you want to spend on your vest, and how much you care about being able to customize every detail of it.
That covers vest basics, but with so many options, how can you choose which storage solution is right for you?
Choosing Your Harness or Vest
The most important thing in choosing a vest, or any storage solution, is recognizing the kind of game you play. If you're playing short scrimmage matches that last ten minutes at most, and you're posting in a position where you don't burn through even a single loader's worth of paint, then wearing a fully loaded vest is going to slow you down and wear you out faster. If you're playing longer scenario games, which sometimes can span an hour or more, it might make more sense to haul around more paint, and more equipment, with a fully-loaded vest. The most important thing with your loadout is to be practical. It's easy to get caught up in all the cool features and functions, but if you want to be happy with your harness, you should pick one that will suit you, and give you what you need to take your game to the next level.