Choosing between New Sectorials

Tunguska is PanOceania with hacking. They tend to be very direct in their play, focusing on gunfighting with skilled troops. They have a strong focus on "elite" play, with their solo Heavy Infantry (Kriza Borac), linked Heavy infantry (Hollowmen), combat characters (Raoul Spector, Perseus, Mary Problems) and line infantry all being significantly more capable than Nomads are typically accustomed to. They're more direct and aggressive with their gunfighting than pretty much anybody, but still possess a decent range of area denial tools (Hacking, Jamming) to project some limited table control. Their firepower is offset by tactical limitations, namely little smoke and no MSV2.

OSS is one of the game's more unique Sectorials, focusing heavily on the power of linked Dakini (possible BS16, Mimetism, 6-4 is massively powerful.) They supplement this with skilled solo pieces, both in terms of midfield combat (Nagas, Posthumans Mk2/Mk5, Dart) as well as backfield support units (Apsara who boosts the BS of all REMs, Shukra who has Counterintel and leadership skills, Danavas who is a great hacker.) Their units are surprisingly reasonably costed relative to their high skill, especially when you consider the point discounts of Posthumans, and cheap orders like Netrods. The high portion of REMs is both an asset and a drawback... Watch out for Hacking, direct template weapons, close combat.

Varuna's focus is on their elite units in the 20s to 30s point range... Elite 1-Wounders who tend to define the capabilities of a Varuna list. Their Core and Haris teams are immensely powerful, but they're still PanO, so don't expect smoke, or much in the way of close combat or direct templates. The plug-and-play capability of their 1-Wounders is amazing, since you can basically pick a loadout of Snake Eaters that adapts to any battlefield role, but the dependence on 1-Wounders means their lists can feel brittle if the battle starts to go against you. Pair those 1-Wounders a strong Core team and defensive tools like Neurocinetic Helots and Jammers, and you can really lock down the table and impair enemy movement. The downside here is that none of these tools are necessarily better than swamping the field with Chain Rifles or mines, something that old sectorials excel at doing, so Varuna has to be careful that the enemy doesn't crack their defense and overwhelm them.

Invincible Army is possibly the most unique Sectorial in circulation. They can be played very conventionally with a balance of cheap-cost units fueling a few massive heavy hitters, but it's very common for them to field a super-charged Combat Group thanks to the new rule Tactical Awareness. Many players have been using a Core link team full of Tac Awareness models and NCO, to get a Combat Group that has 14-16 Orders that can all be spent on the Core link. On the whole, Invincible Army has few cheap troops, and virtually all of them are Hackable, so you need to be comfortable having fewer boots on the ground compared to old Sectorials. They have maximum flexibility in their links thanks to abundant use of Wildcard, and each unit you select will probably need to fill a specific role or capability. Additionally, every casualty you suffer will hurt significantly, since losing Tac Awareness units essentially costs you two Orders instead of the usual one. They do have a fairly diverse range of tools, but because of the cost associated with most models, you'll have to pick a fairly narrow range of units.

Obviously we don't know much about Ramah yet, but I think all of the Sectorials above are likely to be very different from Ramah. They do have some things in common (VIRD relies a lot on 1-Wound units like Haqq does, but completely lacks Ramah's direct templates or super-jumping tricks... Ramah probably won't have the Heavy Infantry presence of Invincible Army, but could very easily have an ultra-aggressive link team in the same way that IA does.)

Ultimately, you should pick what looks cool and is exciting for you. Each of these Sectorials is viable on the table.

 

From what I've been looking at:

Varuna is very 'strange' for PanO, lots of toolboxy units that aren't super-expensive. Lots of Mimetism (or better). But very few 2W models making it into lists (seems to be Patsy the ORC character in a Haris and maybe one ORC HMG/Feuerbach in the Core). It does feel like 'Navy SEALs the Sectorial'.

Invincible Army has a lot of heavy-looking units (obviously), but most of them are NOT 2W. They're 1W+NWI. They average a little over 33 points a model, so it's a bit hard to put an all-HI list on the table (7-8HI and a couple REMs is trivial, though!). As @barakiel said, it's quite easy to get 14-16 orders in a single combat group, that can all be spent through your core link team.

 

It's worth noting that viral ammo aside, out of those units only Zencha can be put down by inflicting a single wound. You won't be able to scare your opponent into shooting downed troopers like it can happen with factions who can provide decent doctor support (more common with REMs and engineer support though), since once someone really goes down, it goes straight to Dead, but that's about it.

And then there are still actual 2W models.