Assault vests and chest rigs are very much personal choice. For those of you who are mainly vehicle borne we would recommend a chest rig. The chest rig is comfortable and doesn't interfere with the mechanics of driving however in hot climates it is not easy to vent. If however you are spending more time on foot then you have a selection of assault vests to choose from.
On choice ask yourself what job you will be doing and how long will you go between resupplies? If your operational and returning back to your main base on a regular basis then a vest that carries maximum ammunition would be a wise choice, but if your venturing further afield, say on a recce, then a load carrying vest maybe more appropriate.