In my experience, whatever the rig might be 'classified' as doesn't matter in the slightest. You can make a belt rig weigh tons, you can setup a plate carrier to weigh hardly anything.
Choose the category of LBE you want based on where on your body wish to carry the kit. For example, I like to have an emergency reload rifle mag and pistol mags on my left hip, so I've got belt setups for that, then a plate carrier to carry the mags to replenish the belt, because I like having that backup ammo on the front of my torso. Some people prefer to have all their mags down on their waist so they'll have just a belt/webbing setup with multi-mag pouches. Or they'll like all the ammo on their torso, so they'll have just a chest rig.
As another example, same goes with water. If I'm gonna carry any I like a hydro bladder on my back, which usually means either a PC or a Chest rig with a back panel (irony being most airsoft 'chest rigs' are replicas of equipment that carries plates), but I find the dedicated PC more comfortable than a CR+Panel setup plus there's a lot more options out there given widespread military adoption of armour and plate carriers with PALS. Alternatively some like a water bottle rather than a bladder, so they'll have a shorter/deeper pouch on the back or side somewhere for that bottle.
Overall, from all the different bits of kit I've tried, something like one of these gives the best all-round compromise between heat dissipation, PALS real estate, weight/mobility and quick & easy putting on/off.
http://www.first-spear.com/product.php?productid=17524&cat=274&page=1
http://www.first-spear.com/product.php?productid=17663&cat=273&page=1
Not saying everyone has to go out and buy FS because it's overkill for airsoft in most situations, I just spend a lot of time on their website. But you can get a BULLE MLE for about £25 (35 in MC) from flecktarn.co.uk and that'll do basically the same job.