Back to the OP - I think gun is the more common choice just it feels more 'fun' rather than having a major advantage over T2.
I mean we have another thread running about how good tml is, and if you can use a few pd's to control more mexes they can start paying for themselves, as well as covering reclaims fields, etc. gun still needs e store and more power built to support it.
Recent balance increased t2 land speed and also added hotkeys for splitting units by tiers, so potential to divert your t1 spam vs gun ACU while your t2 units try flanking. Nerfing ACU range would be way too harsh at late game stage.
What would be a meaningful nerf to gun, would be to reduce the reclaim left by overcharging units, say half normal, then it is less punishing to lose your T2 units vs it