The best way to sum this up is with a quick table of the new stats as they are currently on SiSi. These of course are not necessarily final values, so any speculation you indulge in are your own responsibility.
|Name||1600mm Restrained||1600mm Compact||1600mm T2||1600mm Federation||1600mm Imperial||1600mm Syndicate|
|Armor||4000 (+100)||4000 (-200)||4500 (-300)||5000 (+800)||5250 (+1050)||5000 (+800)|
|CPU||30 (+1)||27 (-1)||35 (+2)||30 (-3)||27 (-3)||35 (+2)|
|Power||500||480 (-20)||550 (-25)||550 (-25)||575 (+0)||525 (-50)|
The first part is pretty straightfoward based on CCP's recent rebalancing. Restrained and Compact offer the same amount of tank, but the Compact is easier to fit. However, you also pay an additional mass cost for the Compact version. The T2 plate is even heavier and harder to fit both in CPU and Grid, but gives a nice chunk of armor.
The second part is the entry of the Faction plates to actual usability. I don't know about you, Gentle Reader, but I've never seen someone fit a faction plate. Why would you when they were less tanky? Now they are going to be the tank of choice for faction ships and other pricey hulls. As a bonus, they're even lighter. Double-plated battleships will now be running double 1600mm Imperials, you can guess. It doesn't hurt that with a dominant Amarr FW zone the LP should be plenty available to get those into the market en mass.
The third part is already being noted as the overall small nerf to armor tanking. Expensive faction plates aside, your average armor tanked ship just lost ehp. Really roughly a Vexor that used to run a 1600mm Meta4 plate will 400 ehp of 18k (2%) of its armor (assuming one ENAM and a DCU II).
Now there are some changes to shield tanks in that posted diff from SiSi, but much smaller. This may simply be because those changes haven't been completed and ready to roll out, so we'll see.
Armor tanking groups beware - you will need to reassess all your corp doctrine fits. Theory-crafters to your fitting tools!