Most of the time the Ammo Depot is worth the points as long as you are aggressive with your units - the more units attacking the more effecient it becomes. Though this doesn’t mean you have to be suidically aggressive. Just be aware that if the depot lasts beyond the first round or two you’re lucky; expect it to die.
The L3/35 is overpriced, but can be useful at taking out support units. Despite it’s low 2/2 defence it might survive simply because your opponent won’t bother with it unless he has nothing better to do. With Speed 4 and Excellent Suspension you can zip around to try and take out any depots or command units. It’s dice aren’t the best, but good enough. I wouldn’t recommend using more than one though, it cuts too much into your army’s points.