The essiential differences in types of hybrid ammunition is the tradeoff between range and damage output. The conventional wisdom (which is particularly relevant with blasters) is to equip the most damaging ammunition (antimatter) and get as close as possible to your target.
However, with scram/kite and range control styles of engagement to objective is to force an engagement to occur outside of your opponents optimal range, and to fit your ship accordingly to operate favourably at that chosen range. Range control is achieved using warp scramblers to disable microwarpdrives, and stasis webifier to shut down enemy movement. Which when combined with superior propulsion on your own ship (typically Afterburner II) you can easily dictate the range of a battle. Hence, using this tactic and the common knowledge that most players equip antimatter ammo only, you can make a more judicious selection of ammunition. Thus moving your ship outside of their optimal, and keeping them inside of yours.
For example. Lets consider that you are fit with 125mm Railgun's, Warp Disruptor II, 2 x Stasis Webifier II, and 1 MN Afterburner II. This will give you favourable range control and you can easily hold your opponent at 10 or 12km with overheated webs. At this range you are best served by loading Uranium charges to give an optimal range of 9km. Placing your opponent inside optimal when in web range, and into light falloff at the extent of your range control... Had you chosen Antimatter charges in this scenario your opponent would be in deep falloff and your high paper DPS figure would simply not be applied to the target. Hence, it is the real DPS at the actual engagement distance which you need to be considering.
With the above example you need to note carefully that you are the one dictating range. There is no sense in selecting a long range ammunition (thinking that you can simply apply damage sooner, and pick them off at range) if you lack the means to keep them there. Your opponent is a proactive and tactically minded person who will not simply allow you to do this. You should plan on a longer ranged engagement only when you have the means of dictating range - and you should also have a contingency for when range is being dictated by your opponent. Hence, you need three ammunitions for 3 different scenarios.
- Close range, good tracking, high damage ammunition to deal with brawlers in close quarters.
- Optimal range ammunition for use when you dictate range.
- Long range ammunition for dealing with kiting ships outside of your preferred range.
For blasters, or tech 1 rails your close range ammo will be faction antimatter, and when using tech 2 railguns you have the option of Javelin. For optimal range ammo this will often be faction Plutonium, Uranium, Thorium, or Lead (in increasing order of range.
For long range ammunition null and spike ammunition can be used in tech 2 blasters and railguns respectively. For tech 1 guns (or when increased tracking is necessary) load faction iridium. Though tungsten and iron do give good range, their damage output is low that you may as well not bother. If you are forced to fight this far outside your guns optimal range you should rethink this fight. Start looking at disengagement options. These ammunitions do have their purpose, but, they are highly circumstantial.
Eg. Loading lead shot into a 425mm Railgun on sensor boosted Battleship with targeting computer to one-shot-kill frigates at 120km can be a lot of fun :)
In addition to faction and tech 2 ammunition you should also carry a reasonable stack of tech 1 ammunition. This is for shooting NPC targets, or damage application over long durations. It also serves as backup ammunition in a protracted fight.