There's a lot of factors that probably would go into this, especially depending on how many rules you tie into the mix, and how much margin of error there is.
Autocannons are probably going to be easier to maintain, but it's ultimately going to depend on who manufactured the gun itself. The autoloader, at least in the real world is an extremely finicky and sensitive piece of equipment, you break that and you basically have to replace the whole gun.
Lasers on the other hand are probably more complex to actually put together, I can actually see them as a relatively low maintenance type of weapon, assuming your parts are of any good quality. With lasers, you just have to make sure the mirrors and lenses focus properly, and then plug it in. Once you get into actually taking them apart and putting them back together though, that's probably when the price is going to go up significantly.
My opinion is that Autocannons will need more frequent maintenance, especially if they've been used a lot. Lasers will tend to need the same level of maintenance, regardless of how much they are used, and will only really need to be disassembled if something goes wrong.
It's also worth noting that if something goes wrong with an Autocannon, odds are that something is going to go REALLY wrong. Lasers, unless stupidly designed (like the Hyper Laser) will generally not want to blow up on you, they'll just heat up.