I'm making some moves to build a tank but It's not clear to me what class I would prefer. Since I'm new at it, I figured my best bet would be to take the most forgiving class. I'm probably doing mostly FP's for now. I'm also thinking there are tradeoffs to make a choice that way, but what do I know ...

hoping you guys can tell me.

In terms of rotation and keeping up the buffs, PT is the easiest one to play. It doesn't have many DCDs which makes it both easier and harder at the same time, as you need to have a good understanding of when to use what (which is true for all tanks, but PT has a small amount of actual DCD buttons, so need to use them carefully). That said, PT's DCDs are mostly just plain DR/defense chance increases, so it won't take long to get used to them. There are some tricks for extra DPS on a PT tank, as well. You can deal extra damage by taking damage but how much you can utilize that will be up to you and healers. PT is the only tank that doesn't have a DCD that makes him completely immune to damage. He makes up for it with very solid passive defenses, and good shielding stats/procs but in some cases you just need to pray to the Shield gods to survive the incoming hits while other 2 tanks can mitigate the incoming damage completely.

Jugg tank is probably the most forgiving because it not only has good DCDs but also has a lot of self heals. It's rotation is fairly straightforward (basically, a priority system where you just use everything that you have until you end up with just Vicious Slash being available and spam that while waiting for other skills to come off cd). It doesn't have as much passive defensive procs as PT, but has overall better DCDs. Jugg tank has a DCD for each damage type but with fairly long cooldowns (PT's DCD are up more often, generally), so you also need to understand which one to use at any give moment. The big learning part for jugg tank is Saber Reflect, figuring out the best places to use it on each boss. If you reflect something big, you not only take no damage but also do a lot of damage. In some cases you can even "walk into fire" on purpose, just to get extra damage for free. Jugg also has Mad Dash which is secretly an amazing defensive that allows you to mitigate huge hits but requires perfect timing and positioning.

Assassin tank is the one that isn't really recommended for beginners. It has a bit of everything that other tanks have - Force Shroud to use against very specific attacks to immune the damage, bunch of generic DCDs to use on specific damage types and also much more micro-management than other 2 tanks, mostly due to Dark Ward. It's also most prone to spike damage, so a bad/inexperienced sin tank can just get blown up sometimes, while a PT or Jugg of an equal skill level would probably survive. Force Shroud is probably the strongest defensive in the game, though, as it allows you to completely ignore certain mechanics/make it easier to deal with them. Currently assassin tank is a bit on the lower side in regards to overall mitigation but simply due to Force Shroud being a thing, it is still a very popular choice.

EDIT: Forgot to add general trade-offs LUL

I'll agree with /u/Equeliber for the most part.

In General

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Powertech/Shield Tech is the most forgiving (and imo faceroll) Tank class there is. Definitely the go-to for beginners.

Sin/Shadow vs. Jugg/Guardian is not as clear-cut anymore to me. It definitely used to be that Sin/Shadow was the most technical, but with all the changes I would say their are on similar footing.

Jugg/Guardian has slightly more leeway because they have more armor and the Barrier from Force Scream/Bladestorm. But overall if you're not good about being on top of your DCD's, knowing when to use which ones during each fight, your healers will hate your or you'll just die.

As much as Sin/Shadow is maybe slightly more difficult than Jugg/Guardian -- I have heard many people say that once you learn Sin/Shadow it is smoother to run than Jugg/Guardian.

Tradeoffs

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Powertech/Shield Tech

- Pros: Very easy to play. Being easy mechanically means you can focus more on your positioning in the fights. Highest Absorb %. High Base Armor. High DPS (for a tank). Hydraulic Overrides cheeses some of the knock-around fights. Resource regen for just being a tank.

- Cons: Low number of DCD's, so you have to pick and choose when to use them in the more difficult fights. Boring (imo - just due to the lack of things you're actively doing as a tank)

Juggernaut/Guardian

- Pros: Highest single-target Threat opener. Five DCD's (6 if you are actively using Roar's 15% Melee/Ranged AoE DR) means you'll always have something up if you're managing them properly. Highest Defense Chance with Blade Barricade being up 100% of the time. Self-cleanse (with appropriate Utility).

- Cons: Have to keep track of which DCD's do what, and meter them out appropriately over the course of fights. Lower Shield/Absorb %'s than any other class. Building and maintaining Rage can be cumbersome in fights will little-to-no AoE damage going out. While you can initiate AoE Threat, this class is abysmal at maintaining AoE threat.

Assassin/Shadow

- Pros: Force Shroud. Highest Shield Chance. High Absorb Chance. Built-in Endurance buffs. Self-cleanse. Force Shroud. High, if not highest, AoE Threat generation (and ability to maintain it). Same as Juggernaut/Guardian - lots of DCD's so you should have one up whenever you NEED it. Resource regen for just being a tank. Did I mention Force Shroud?

- Cons: Very mechanical to run, has a bit of a learning curve. Lower armor than the other 2. Even though you get Force back for dodging/shielding, if you're spamming you can run out pretty fast sometimes. Both of the highest mitigation abilities require you to monitor stacks properly and refresh at optimal times. Keeping track of this amount of stuff can make tracking the fight more difficult if you're not accustomed to multi-tasking on that level.

Honestly I do not play Powertech or Vanguard tanks because IDK what to do when I'm about to die lol. However, I know with Juggernaut I can pop Enraged Defense or Enure or use Mad Dash or use Reflect or Saber Ward or my CC breaker or something!

I think Powertech is the only tank that does not have any way to replenish its HP. so no thanks lol. Assassin tanks aren't as hard as people make them out to be. Yes, they are harder to master but I've not mastered a single spec in all the time I've been playing SWTOR, and yet, i can tank, heal and DPS just fine. I've even done some MM Ops lol.