Update...!
So, made it to very late game. A summary of my findings follows.
Turns out that my playstyle (long range combat and saturation fire) suits EP rounds over particle beam rifles and blasters, and needlers. The HMG with EP rounds kills all with ease, even at long ranges, making it way superior to the innacurate and high TU requirements of the particle blaster. Possibly thr particle blaster could be re-classified as a close combat weapon, as save for the pistols, there is little in the way of progression for that soldier class save for moving to plasma blasters from flamethrowers/shotguns, and the occasional plasma blade bezerk charge. The heavy needler is also less fatal than the HMG EP rounds, even if it is more likley to land a hit due to sheer volume of fire.
There is little to choose between the EP loaded assault rifle and Particle rifle, though the devastating full auto fire mode of the assault rifle for close up violence gets it the nod over the slightly more damaging in single shot and burst mode particle rifle, with its slightly worse accuracy and occasional lack of an ammo supply. Manufacturing EP rounds in abundance is proving to be easy if I keep a steady stream of UFO's being dismantled. Particle pistols have too spotty an ammo supply to be useful and are horribly innacurate compared to the laser pistol, even when firing the laser pistol on burst mode.
Hybrid rockets are very much fun, and the antimatter railgun rounds live up to thier billing - way more fatal than the coilgun. I have found little use for gas grenades - they play the same role as incendiary grenades, and the time spent producing them is better served keeping my EP round stock up. By this late stage I dont really need stunned aliens - I have 2 facilities full of live Taman and Sheevar.