As of right now, no, there is no reason to develop personal energy weapons. The amount of effort you'd have to put into having them simply on par with rifles would require some very advanced energy sources that we don't have access to yet. And as stated, having them on par with lethality, but massively more expensive, makes them inferior. It could come to a point that the kind of portable power source to produce something equivalent to a rifle, but can fire all day without reloading, becomes inexpensive and easy to produce, and that might make a positive trade off, but that'd be a long way off.
It would have to be easy to maintain, too, which has already been a problem with conventional firearms in the past, and only becomes more of an issue as weapons get more complex. AKs aren't ubiquitous because they're great rifles. They're good, but they're popular because they're easy to use for untrained personnel. Also, because the Soviets sneezed them en masse to anyone that looked at the west funny, but that's another issue. There's a lot of other assault rifles that are far superior in the hands of a trained soldier, but the training is the caveat. I can only imagine the issues with keeping an energy rifle in working order.
There's also other issues that may come up with a directed energy weapon that are unique to their specific function. Unfortunately, we're probably never going to get proper laser guns as personal weapons, because they will fucking blind everyone. Even laser lights that you use to play with your cat can cause eye damage if you look right into them for too long, and far before you get to the sort of power output in a laser that will make in comparable or superior to a convention rifle, just seeing the light reflected where the beam hits a surface will be enough blind you faster than your blink reflex can react. And using UV or IR is not a solution, unfortunately, because the light is still there, regardless of whether you can see it; if anything that's more dangerous because of it. You can equip soldiers with eye protection, but it's still an extra risk that you're presenting, on top of which that will severely limit your areas of operation. You can't use them where there could be any non-hostiles, since you're going to fry out their eyes, and even blinding the enemy en masse might be considered a war crime, and you likely can't use them in low light conditions, since the eye protection itself will handicap your soldiers.
There is the issue of stopping power, too, which could vary based on weapon type. If there's no projectile or kinetic force, then it could have issues with bringing down an attacker in a timely fashion, even if it proves to be lethal, the same way that militaries have had issue with low caliber weapons before. This might make projectile weapons that use other means of accelerating the projectile, instead of gunpowder, like a railgun, more likely, but they would still have the immense energy needs, so we're not seeing that anytime soon, either.
There is some potential for non-lethal weapons, but so far as I know, most of those have been relegated to mounted weapons, too, like sound guns. There's been attempts at hand held designs, like the
PHASR, but so far as I know, there's not really any personal, non lethal directed energy weapons that have really gotten through testing and gotten any broad use. And again, existing technology, like tasers and bean bag rounds, work rather well.
