Large Lasers aren't at all horrible, but the game system really incentivizes large chunks of damage over smaller chunks of damage (PPC to the head is a crit roll; LL to the head is not; 10 damage in one location is more likely to 'cause a crit roll than 8 in a vacuum). As such, PPCs generally win out, for my money.
On a damage per ton scale, PPCs are more efficient, doing .7 damage per ton of weapon vs the LL at .625, with identical heat per damage (i.e. 1:1). And then the extra range for the PPC, and larger chunk of damage pushes it over the top. Yeah, the PPC has a minimum range, which will occasionally be a hassle (and the LL never needs to worry about that), but you can always just walk backwards (or run forward and twist) and the minimum range ceases to be an issue. It isn't at all difficult to never suffer from the PPC minimum range penalty.
Like, if you are planning on being inside the PPC minimum range, you might as well be using Medium Lasers instead of Large Lasers. If you are planning on shooting at outside of close combat ranges, PPCs are the way to go, generally speaking.
Again, Large Lasers aren't at all horrible, but give the choice, I'd generally take a PPC over a LL (assuming I have a choice and control over the design of the mech). There are certainly mechs in the 3025-3039 era that could totally benefit from replacing PPCs with LLs, but that is 'cause of the design of the mech rather than because LLs are generally better than PPCs. Yeah, taking a Warhammer and replacing the PPCs with LLs (and armor?) is going to improve the Warhammer. But so will leaving in the PPCs and pulling out some of the other non PPC guns (MGs, SRM6?) and replacing them with armor and/or heat sinks. But then, to be fair, two of the best cannon mechs of the 3039 era are primarily armed with LLs (Wolfhound and Crab). So at least there is that.