[FSN] So I ship Rin/Archer and Rin/Shirou the same because I suspect what makes her fall for him hasn't changed between the two. Saber/Shirou vs Saber/Archer, though, is an entirely different matter.

Ignoring the methods in which each gets romanced

Saber and Shirou are the same, essentially. They have ideals that they cling to firmly, regardless of what anyone else believes, or how much pain it brings to them

And they would both rather hurt or die themselves than any other person

They are very much alike, with Saber being more experienced and Shirou being more...fresh in his ideals, passionate and not yet beaten down by reality.

They balance each other out and work well

Archer has betrayed himself and lives a lie where he pretends he's given up his ideals and hates himself for not doing it

they're similar in that they both want to destroy themselves, essentially, but Emiya wants it for primarily selfish reasons, while Arturia does for selfless reasons

(Yes, Emiya killed many people, but he's saved countless more and even saved the world.)

They are not compatible without Emiya reverting back to his Shirou self, and Saber lacks the ability to make that happen

So I don't dig Saber/Archer

Rin's feelings are probably more simplified in that he's something to believe in, someone she can depend on. She can jump off a building without doubting that Archer will catch her, and jump into battle

without doubting Shirou will be there

I MEAN IN THE UBW ANIME IT'S ACTUALLY KIND OF HILARIOUS

Archer 'betrays' her and not five seconds later Shirou CRASHES IN with Archer's swords as her replacement servant

Archer and Shirou don't interact as a unit when dealing with Saber, because their interactions are so fundamentally different when approaching her

with Rin, that's basically what she's got.

Arguably from the moment she summons Archer until the end of the war, she never stops having the exact same Servant, she's just gotta mana transfer to boost his power there in the middle

and they generally react the same to her behavior and etc.

That's why I ship Rin with both incarnations of Shirou just fine, even though the characters are quite different, but no Saber with both.