Heavies have 100 extra HP, infiltrators have 100 less HP.
No they don't.
All classes have 500 health. All classes but infiltrators have 500 shields. Infiltrators have 400 shields.
HA get an overshield that grants either 700 health (NMG/AS) or 45% damage reduction (RS). Note that with the first two there is an activation cost when you turn it on and the health granted ticks down with time while switched on, so only about 600 of that health is usually going to be effective in many situations, dropping lower if you keep it on for longer. That is still a >50% increase in effective health if you have need of it, so overall you will have more than if you are using resist shield.
This is even more true if you are using either nanoweave or flak armour. These are both additional resistances that do not stack with resist shield (only the highest resist value counts). These
do stack with the NMG/AS additional health, making that bonus 600 worth even more. I'm loving flak/NMG against lolpodders, even if it's not as obscene as the ancient resist+flak when that stacked additionally. Direct hits mess you up, anything else tickles.
Note that NMG is most effective as an oh-shit button when you get caught out. It is actually more valuable than your shields, as it regens far more slowly and is usually a one-off type of deal. Paying multiple activation costs for pulsing it on and off as you run is burning effective HP that will take ages to come back.
If you want consistent tanking ability then resist shield with advanced shield capacitor (and optionally some medical kits) gives you a repeatable edge over most enemies. Always being on full health with a 45% damage resist is a nice loadout, provided you have a weapon to take advantage of it.
Incidentally, making out like a bandit during these sales. So far;
Cosmetics:
Three new camos; Esamir Snow, Forest Ground Infantry, Giraffe (got friendly fire within 10 seconds of putting this on, TKed twice in the first five minutes)
Two helmets;
GD Titan for LA (has complete camo coverage of the face) and Nightstriker helmet for every other class
Flash icecrusher tyres. If only they worked...
EM6 LMG. I'm mostly running this in cheese mode; extended magazine and 2x reflex. 200 round LMG which is reasonable at mid range and can just about be hip fired. Not bad, but I generally prefer the SAW at range and it is still lacking at close range. And yes, I've played with attachments in VR and need to actually kit it out properly, but still not the best gun in the game. Might just go with the traditional compensator and forgrip and run it like a weaker SAW as my mid/long range weapon, but lacking that perfectly accurate first shot that the SAW has (not to mention the 200 damage...) makes anything feel worse at range than that beast.
Decimator. I've mostly switched to this on my HA over my Shrike. This came after I direct hit a BR100 in his mozzie and he didn't die to the Shrike rocket (activated fire suppression and flew away to repair). The Deci instantly killed him once he came back. I'm not completely used to the drop on it and it's hard to see the extra damage against most targets, but I think it's a permanent lock on the slot now.
Vanguard Walker. I doubt I'll pull this all too often but it's a nice option. I have gunned in a fair few of these since the sale and it's a nice weapon. Landed a fair few air kills and you can do a decent job against infantry, especially when they are trying to pop you from a ridgeline. I think it's actually better against infantry at range than the Skyguard (tighter COF to make up for no flak bursting against air). Also does a shocking amount of damage against armour (most notable Sunderers and Harassers) if you can line them up.
GR22. This is the closest NC come to the disgustingly good TR assault rifles (I don't really understand TR players who aren't 24/7 medics...). Burns through ammo absurdly fast but tends to shred anything you point it at, ADS or not. I've kitted it out for full CQC (advanced laser, 1x reflex, SPA) it outperforms the NS-7 PDW I'd been trying to make work on my CQC Medic. It feels a lot closer to the Blitz than the PDW did, and that is a good thing. The recoil does hurt mid range more than it did on the SMGs (ironically) but I'm starting to get a feel for bursting with it.
Sunderer Fury (rear). Meh. I mostly prefer the Basilisk for an all-round weapon. But nice to have options.