With the new Matched Play rules for reinforcements there will be a meta change in how summoners are used. Unlike the mostly used SCGT where you get extra points if you summon, Matched Play uses a system where you hold points from your main list back to later deploy however you can, whether that's summoning or an ability that creates a new unit.
Reinforcement points aren't assigned in the list building phase. What this means is that you can have an allegiance list of 1500 points to one faction and save 500 points to reinforce with new units from separate factions if desired.
The main difference between the types is that summoning requires you to successfully cast a spell then you can deploy a new unit within range, abilities tend to require an easy roll or no roll at all and then units enter the game by some method (from a board edge or Realmgate).
Both have their uses within the game, the ability based reinforcements are more reliable, but less tactical. Whereas the summoning based reinforcements are less reliable, but more versatile.
Here are some alternate tactical uses for reinforcements rather than just getting more bodies on the ground:
• A Unit is protected from damage until deployed to the battlefield. Although if all your reinforcers are killed you lose the unspent points.
• Use reinforcement points to react to the current tactical situation rather than playing all your cards early. You can deploy either an anvil unit or a hammer unit depending on what you need after a few turns.
• Deploy a unit on to objective at critical moment. This can literally be he difference between a win or loss. Most Pitched Battleplans only require five models nearby to claim an objective.
• Deploy a small unit to act as a blocker or chaff. Death excel at this with their availability of cheap units like zombies.
• Deploy slow units at long range to get behind enemy lines quicker. Slow moving Fyreslayers can use Magmic Tunneling to get a unit behind the enemy lines.
Using reinforcements has to be done carefully or you risk throwing away valuable points and putting yourself at a disadvantage. To ensure this doesn't happen use the following tips:
• Take at least one unit which reinforces with an ability easily or automatically, even if it's not as useful as the summon able ones, this is your back up if your spells don't succeed.
• Don't just rely on a single wizard to summon units as you can only attempt each spell once per turn. I would suggest a minimum of three separate reinforcers for redundancy.
• Have a wide variety of summon able units, plenty of easy summons such as zombies and only one or two hard summons like Bloodthirsters.
• Only use reinforcement points if you really need too. Don't do it just for the sake of it, have a plan.