OK, new gunslinger in RG27, the -3ERD. Somebody looked at the previous gunslingers and said to screw the electronics, make it tough.
They succeeded. Armor is the same – just in Ballistic Reinforced. Case II on the gauss rifles means that after one goes off the atacker still has to tear through any remaining arm internal structure. A clan-tech XL engine massively increases the average lifespan by itself. The loss of the ECM means that it is fractionally more vulnerable to a couple things and an XL gyro increases the chance of bad luck being really bad... but I’d expect an IlClan era Gunslinger to be active turns after an invasion era one would have fallen.
Speaking of Clantech, you remember the medium or ER medium lasers on the old versions? They’re now clantech ER mediums, a massive increase in both range and damage. The old smol laser on the -1ERDs head becomes a small X-pulse, for eXtreme infantry clearing, and the rear leg lasers become a pair of same; mooning an infantry platoon is a reasonably practical tactic, especially as SRM infantry are going to have a nigh-impossible time getting through the armor.
You lose a ton of gauss ammo (going down to 16 turns of fire,) run hot with only 10 DHS, there are no electronics, and BV goes up by hundreds of points. I still think I’d take the upgrade version.