The first question that comes to my mind:
How is the energy stored? The US-Navy just equiped some battleships with laser guns and their biggest disadvantage is the charging time. You need to store the necessary energy, if you can't produce it fast enough. There are a lot benefits over projectilweapons, but also disadvantages, keep that in mind.
It's very unlikely to carry a mini-nuclear-reactor in your handgun, so you must store it.
Which requirements must the storage suit?
Fast energy release. You can't be lethal if you give a view watt per second. This is really the biggest problem today, how will your future guys solve that?
Small, the smaller the better until, lets say the sice of a cigarrbox per 20-30 shots, at least.
Fast energy release:
A storage that we know today which can release energy very fast are capacitors. These have problems which make them unsuitable for our purpose, like an energy drain over time and small capacity.
Batteries cannot release energy fast enough.
Fuel cells could be a solution due they could set high amounts of energy in very short time but are technically very complex, depending on the fuel. Due we are in SCI-Fi here, our todays problems can be solved in your setting and the complexity might not be a problem anymore.
Biggest Problem of today with fuel cells are heat and low efficiency, but that has been the same with OTTO-engines 100yrs ago, so what...
You want your weapon to be handable by small woman hands. For home-defense very small pistols are not uncommon and you must try to fit that requirement. It's not necessary to provide 50rounds if an average person cannot hold the weapon, 5-10rds are good.
One container or cartridge?
Both have their advantages. As it has been said, for military purpose, where a lot of shots are fired in a short time it is essential for the safety of the gunners that there is no delay between triggering and the shot. But in home-defense you don't have to spray a lot of ammo, a few rounds is good to strike back an attacking person.
So far booth, container and cartridge fit the requirement.
Advantage of container:
You can just fill them with the needed chemical, its basically a fuel-container and thus easy to use.
You have only one source of errors here, not like cartridge. Every cartridge could be damaged and block your weapon, even if the next one is fine. This is both, an advantage and a disadvantage, if you have a jam with your cartridge just release the magazine, unload the blocking gardridge and reload. To fix a broken tank might not be that easy.
Advantages of cartridge:
The handling of cartridges is easy but a little work, if you have ever loaded some magazines, you know what I mean.
Error sources are plenty, like I wrote at the Advantage of containers.
But what makes cartridges really good is the fact that you can load various cartridges!
It's not unusual in military purpose to load some tracer bullets at night or AP-cartridge if some enemies might wear bodyarmour. You cannot know what comes and thus different cartridges are a high benefit!
Especially with energy weapons. We are talking about home defense and you don't want to kill someone but might tranquilize the attacker. If you have 10rds in your magazine, you can load 5rds tranquilizer, 2rds lethal if the tranquilizers don't work for any reason and if in the worst case the attacker wears body armour 3 further shots of armour piercing ammo. Or whatever you want.
For me, cartridge is the winner!