So for 300 xp what specs would you choose for maximum defensiveness? Armorer, s. Defender, m.a. with coordination dodge?

Depends, 300xp is a little bit tight on the budget side, but personally I would go with Soretsu Defender, with basically the full tree + Sense as force power. A true lightsaber monkey for the group with strategic form. 3 Ranks for reflect, 4 ranks of parry, 4 upgrades against incoming melee checks and with strategic form the ability to force people attacking you.

A true guardian of the party. Adding protector second for circle of shelter and armor to round everything up sounds good, but taking a lightsaber spec with some extra ranks in reflect and force rating lika Niman sounds very interesting as well. Depends really how you want to develop your force powers and if you prioritize afterwards group security or personal one. Niman is imho a fantastic lightsaber spec as well, but even the offensive defense abilities from the arbiter are actually quite great, because spamming sunder to disarm any dangerous opponents is an actual very cool and effective move for a character who focuses on defense.

Still in general the question is the wrong one. The real question is: What style of defensive character do you want to PLAY? The sword and shield style of the protector with his circle of shelter, the trolling Obi-Wan style which catches all the attention and hate of the enemies with intelligent use of your wit and lightsaber or the cool and efficient way of the armorer who can enhance the dense of the group immensely if given enough time and resources for his crafting, etc

Sure, some of them are mechanically different and not equally efficient on all fronts, but what is more important is that they all represent a vastly different characterisation, because they approach problems vastly differently.

Trandoshan Hired Gun: Marauder/Gunner

5 Brawn; Toughened and Feral Strength from both of the first two rows, then Lethal Blows, weave down to the first and second Enduring, Defensive Stance, and Dedication - Brawn 6 (175xp). Add Gunner; begin with Durable and weave through left side of tree to pick up both Enduring (125 xp)

27 Wound Threshold, Soak 10 without armor (so any armor worn would count as soak against a standard lightsaber), Brawl 1, Coercion 1, Discipline 1, Melee 2, Vigilance 1 isn't a stellar suite of skills, but it's likely to get the job done long before the character is dropped from what will likely be the bulk of enemy fire. Claws do 9 damage with a critical rating of 3.

This character is lethal and able to shrug off almost everything with zero equipment.

That's what I like for defense.

5 hours ago, JRRP said:

Trandoshan Hired Gun: Marauder/Gunner

5 Brawn; Toughened and Feral Strength from both of the first two rows, then Lethal Blows, weave down to the first and second Enduring, Defensive Stance, and Dedication - Brawn 6 (175xp). Add Gunner; begin with Durable and weave through left side of tree to pick up both Enduring (125 xp)

27 Wound Threshold, Soak 10 without armor (so any armor worn would count as soak against a standard lightsaber), Brawl 1, Coercion 1, Discipline 1, Melee 2, Vigilance 1 isn't a stellar suite of skills, but it's likely to get the job done long before the character is dropped from what will likely be the bulk of enemy fire. Claws do 9 damage with a critical rating of 3.

This character is lethal and able to shrug off almost everything with zero equipment.

That's what I like for defense.

Sounds Like my "Bulk"-Nikto PvP char ^^ - so be aware of Thermal Detonators... a frustrated GM will pull them out if your Char seems to be immortal to all standard means.

In the end this would be the damage soaking Tank, with later on the unmatched protection trait (usefull to help your Team), but this relys heavy on DP use (as well as adding M.A. for the coordination dodge)

Then again the Armorer lets you start as a Forcy and will give you a FR of 2 that will be usable with sense "commiting" Def-Upgrades while still have a free FR for enchance or force talents. - Unmatched heroism is here quite the same as Unmatched Protection (different is the damage reduction therefore he get engaged with the alli)
Armorer will boost the use of armor (and the building of those)

Protector helps to help the party more than yourself (the nobel sacrifice way of doing things ^^) - the trouble here is that Force protection can't be utilized much if you also want to use sense... well as long as you don't have a second tree with Force rating at least. - Improved Bodyguard (as well as bodyguard) will work nicely with Unmatched Heroism since it allows to engage the ally, and then protect them.

Soresu Defender then is the most offensly Force Tank, with a provocation ability (strategic form) and relying heavyly on parry and reflect while dishing out counters. since Soresu has no Force rating it will need a second force tree to utilize Sense in addition to "strategic form"
Since Soresu is the "Intelect"-Lightsaber form you will suffer in the "Brawn" to bring up you natural soak (and starting wound threshold) so this tree is really heavy rellying of migiating Before soak, and wouldn't work to well with Protector. (At least not at 300 XP later on it will be a great addition)

In each case armorer should be a part of any "Tank"-combination ether Protector/ Armorer to migiate the damage dished out to your Partymembers (without dying yourself)
Or Soresu/ Armorer to provoke the enemys and counter them (without dying when you fail to migiate all damage)

In each case Sense should be a part of your build to gain a additional benefit of Upgrading at least 2 enemy checks. (Protector/ Armorer will lend you a FR of 3 in the end, and Soresu/ Armorer with an FR of 2)

The benefit of the force combinations is that you will start with the Force, and that the combinations are IN-career which will reduce the activation costs of the second tree, and you won't need to rely to heavy on skills except Lighsaber.

The benefit of the non-foce combination proposed @JRRP is the real high Soak and WT, therefore your Strain will be a real pain in the ***. (you'll have to think twice if you realy want to use a second maneuver) and if you want to get to higher damage output combinations and gain some defensive means beside soak you need a third tree like M.A. and therefore you'll need to concentrate a bit more on an extra skill besides brawl, you need coordination to utilize coordination doge and martial grace. therefore you won't get any means to boost your attacks (no accuracy or other handgrip upgrades for brawling unarmed) and if you go for M.A. you shouldn't go for Meele.

There are truly tons of ways to be a defensive character. With my build (which I consider to be a little ridiculous, to be fair), I would equip the highest soak armor I could get my hands on, as well as a vibro-ax or sword with custom grip, balanced hilt, etc.

That is, of course, entirely dependent on the makeup of the rest of your group. If there were a lot of incredibly squishy characters, it would make more sense to pick bodyguard as the second spec and try to soak damage that way.

If I were going to play the character, I also wouldn't put all my ability points into Brawn, but I like being a bit more well-rounded.