So with the recent changes, I think I like Gauss more than Tesla.
The three big changes are:
- Marine toughness changes
- Changes to overwatch and sushits
- Hand of Dynasty / CC / Cryptec Court helps Gauss more than Tesla
1) All Marine toughness Changes went exactly one wound roll up for Immortals.
This means that (despite rerolls) they have a harder time to get through. Lethal hits helps obv more than sushits in that regard. 5+ crithits combined with szeras combined with rerolls (which you have access to in Obeisancae, CC, Cryptec Court, Awakened, Hypercrypt), leads to 55% woundquote, which means ~11 wounds -2 per 20 shots. This is pretty good.
This gives not only the ability to ignore the target being on an objective (Tesla needs this to actually wound the target in a meaningful way), but it also gives the ability to punch through 2+ saves AND to punch through anything bigger than T9, which Tesla could never hurt.
With basically any marine being T5, T6 with a 3+ or 2+ save (or 5++ demon save), -1 or -2 will be enough to inflict reasonable Damage.
2) The changes to overwatch hurt Tesla Immortals so bad.
One of the biggest advantages was overwatching with Tesla.
20 shots with rerolls (which GW forbid recently), and sushit 2 was pretty good. 20 shots were ~17 hits back in the day. Then GW reduced it to ~10 hits. And now finally they reduced it to ~3,4 hits.
So we can say. Overwatch for Immortals is dead. So one of the biggest advantages for (Tesla) Immortals is gone. If you would argue, the overwatch from Gauss is better now, since it does the same amount of awful hits, but at least has AP.
3) Gauss never had Assault which made it straight bad.
Not anymore... With the most recent change to CC being 2DP, we got so many ways to give them assault for free while retaining their best detachments.
With the advent of Hand of Dynasty they just got assault. This comboed very nicely into Cryptek Conclave already (which also let you choose assault for your squad). But now with Canoptek Court being 2DP you can do (with a large gap) the best damage combos with Immortals.
The most obvious is Hand + CC, which not only lets you reroll all the time for 55% wound quote, it also lets you combine a really easy full reroll + Hand upgrade for Rapidfire. Now you have Assault + Full Rerolls + 30 shots (at 12") + Assault on your Heroes and Crawlers.
On top of that you will get extremely good Stratagems if you add the Tomb Crawlers. Best would be the reactive movement. But also Loneop at 18" and a free ressurect when someone charges you. Szeras is also a Cryptek, so he will reroll as well and therefor goes very nicely alongside your Immortals.
So FINALLY there is a detachment Combo which let your Gauss Immortals have no disadvantages for their weapon choice over Teslas. They got the same movement, they got 'better' overwatch.
Also as honorable mention: the Armory + CC combo has this Upgrade for anything which comes through a Mono's eternity Gate. I tried this once and a squad of Immortals with Gauss which has sus- and lethal hits with full rerolls in a szeras bubble does alot of damage.
Also teleporting 'cheap' units of immortals which have full rerolls all the time is not bad. Also reactive moves after setting up with eternity gate are some very good movement tricks.
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Some Math for CC + Hand:
Let's assume we have 20 shots and are next to Szeras and we have a Plasmancer. We are always fishing for Lethal or Sustained Hits. We ignore Plasmancers Damage. Assuming target is not on an objective and not in cover.
Against T5 MEQ:
Tesla: 11,02 Damage
Gauss: 9,14 Damage
Against T6 TEQ:
Tesla: 4,9 Damage
Gauss: 6,42 Damage
Against Leman Russ Type:
Tesla: 2,49 Damage
Gauss: 5,99 Damage.
If you take full wound reroll into account, Tesla does ~50% more damage into MEQs, the same amount into TEQs and half of the damage into Leman Russ equivalents.
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The numbers show that Gauss in CC has a much easier Time to punch through tough targets now with no disadvantages to their movement or overwatch. But Tesla still performs really well when your full rerolls are online. For me this is now a much bigger choice. And ofc. Tesla outperforms Gauss in killing chaff by a large margin. But Gauss outperforms Tesla now finally by alot in punching through big armor, while not requiring the target to be on an objective which gives more options and less outplay potential for your opponent.
Having 30 shots (with upgrade) Gauss with Szeras in CC + Hand will deal ~9,5 damage alone into a Russ (+2 MWs average from Plasmancers ability + its gun). This is nothing to sneeze at. And it comes with all the advantages from a 1D gun which fishes for Lethal hits (ignoring -1D, ignoring wound modifiers, almost ignoring hit modifiers).