Oh damn that’s a rough one! But I think the answer here is Toge. Here’s why:

Rika’s & Yuta’s relationship was very much a young reckless lust - yes Yuta did love her but they didn’t really get to live hardships in the real world. Their relationship was made out of silly dates, Yuta sneaking in her room and Rika always getting her way. That relationship was also driven forward 99% by Rika with Yuta just tagging along, infatuated by her. Would they have lasted had she not died? I actually don’t know…

But with Toge… that’s a much more mature love. It didn’t start at lust or status thing. It started as a friendship, a mutual understanding of each other’s lives, mutual interests, mutual likes. Yuta doesn’t luat after Toge because he’s a hormonal teen but because he genuinely loves Toge as a person. That’s why this relationship is stronger. That’s why Yuta would still chose Toge