I like working with the plastic glue
Yeah, everyone's got their preference for sure. I've been known to bust apart even painted models to revamp for current rule sets/effective loadouts that are done with being proxied.
Gotcha I suppose, so if narrowed to the two I want, you'd say the CML?
Will also say I wonder about your Command Squad, I thought it wasn't legal to put a CML on a Hammernator or an Apothecary?
4x TH/SS (one for each model that isn't the Apothecary), one model from those equipped with a CML, and the Apothecary as they must be. Easy to miss with the way I typed it, forgive my shorthand.
most I've heard discuss Imperial Heavy Weapons seem to hate the Plasma Cannon for the unreliability of Small Blasts mostly
Small blasts only become unreliable when your opponent know how to, and consistently does, space their models appropriately.
which resonated since I know I'll be facing Nids and Guard
There's crucial info right there. If you're facing horde armies hells yea, CML all day. I'd still stray away from the AC though since it's 20 points and honestly just doesn't cut it without twin-linked for me...though as a BA player primarily I'm spoiled with TLACs almost everywhere I look.
Seems like it'd only be better against massed MEQs and TEQs, with the other two better against horde infantry and vehicles.
You're half right. The PC is for sure better against T/MEQ, but it does the same amount of damage to GEQ and worse as well...just without the second blast (or points cost, CML blasts are also S4 which can leave you wanting sometimes). ACs are a joke against vehicles at S6 even with Rending (being that the AP2 factor of Rending doesn't apply against a vehicle). The potential is there, but in all honesty you're just not stacking the odds enough in your favour and Guard is pretty much all AV12+ with few exceptions unless you're flanking and Terminators are hella slow. CMLs can do damage to a tank, but with AP3 you're almost never going to wreck anything in one turn; you'll end up putting two different squad's CMLs (50 points of upgrades) into the same tank just to get results. Again the potential is there in that you could get two pens and two Immobilized results, but in all the time I've used them I've never had that happen to me. The S7 from a PC has a rough time dealing with tanks to be sure as 5 to glance AV12 is nothing to count on, but AP2 is where real anti-tank starts with the current Damage Chart.
Against AV12 and 3HP (based off attacking a Chimera's front armour)
-CML has two shots at S8 need a 5 to pen and can't wreck a vehicle without both coming up Immobilized
-AC is pretty much the same, but needs a 6 just to enable Rending and then at least two 6's again to wreck
-PC needs a 6 just the same, but can blow up the vehicle with its a single shot