I voted MOLLE (and would specify a preference for MOLLE II vs having to use MALICE clips), and here's why: panels were originally on LE vests, but even they have gone towards MOLLE now. Point in case, there's a lot of MOLLE pouches (and gear) available for relatively cheap, whereas panels is almost like buying into a proprietary system.
The Cons for MOLLE... pricing, maybe, they're cheap but it ads up. Heavier? They're pretty light, and when you consider a lot of players are going towards things like plate carriers and full armor now, the weight is negligeable. Reconfiguration time, I dunno if anyone actually reconfigs on the field; the only scenario I can think of is if someone ditched their hot/heavy armor, but I'd just say put some of your mag pouches on a leg panel or something, instead, if you plan on ditching your armor.