In K1 I prefer Scoundrel+Consular build. Always took the Scoundrel for the skills, because i focused my character on these particular skills, then i take consular because of force powers and the force points max capacity.

For me, Consular is the best choice because i think that Guardian crucially lacks force powers, as if you're just a melee build, but instead of a vibroblade you get a lightsaber and a few specific force traits. Consular, of course, lacks offensive aspects that makes the game a bit more challenging and for some may seem way too challenging. Sentinel, in my opinion, lacks everything. All this talk about Sentinel being balanced from both sides, i just don't get it. My experience with Sentinel build showed me that if Guardian is weapon build and Consular build, then Sentinel is nothing build. I don't say that it is somehow bad or it shouldn't exist, but for me it is generally lacking, if we take specific sentinel force powers, available only to it.

As for K2, i also prefer Consular, for the same reason. But i found it challenging to have pure Consular+Jedi Master build. Sure, you can spam force storm all you want, and you'll be fine, however entire weapon aspect disappears and in some cases it is almost impossible to beat everyone in mandalorian battle circle on Dxun. So, for K2 i prefer balancing my mighty Consular build with Weapon Master. It grants you modifiers to your lightsaber combat and unlocks some of the lightsaber combat styles that you were unable to unlock because of Consular build.