Dear older, married men, and everyone else, too--Which ages better, women's boobs or women's butts?

I'm especially interested in hearing from older men, or men that have been married for a while. Please let us know how closely you fit the bill, if you're sharing some advice. So here's my question: given a choice between the two women I'm about to describe, who would you choose for a serious, long-term relationship?

Assume that you like butts and breasts equally, and that you strongly prefer big breasts.

Girl A: A 25 year old woman with amazing, amazing boobs. They sit up nice and high and perky. They're nice and big, at least definitely bigger than 34D, but not obscenely huge. Grapefruit-sized. And they're firm. You can squeeze them nice and hard and they feel just right. Just the best fucking boobs around. Borderline perfect: 9.5 out of 10. However, she's got White Girl Butt. It's just a little tush. It's not big and round. It's not truly small, but it's barely a handfull. So I can grab on, at least. And yes it's cute and she doesn't look terrible in pants. But she doesn't have enough curves in the hips/booty region to make me gush with joy/pride: 7.25.

Girl B: a 25 year old woman with 34D's--but her boobs are squishy, not firm, so they flatten and spread out, and pushing on them and grabbing them doesn't feel as good as it could. It's a shame, really. She looks great in clothes, though, including lingerie: 7.75. But on the other hand, her ass is just beautiful. It's nice and big and round. It's not too big, either--though I wouldn't mind if the roundness were filled out just a tad bit more. Gorgeous and supple, a pleasure to squeeze and slap: 9.25.

Assume everything else is equal. Which body is better in the long term?

I know that breasts lose their perkiness and get saggy. But what if they're already flattening out into pancakes when she's lying flat on her back at the age of 25? How low can they go? Is Girl B's chest going to be really gross at the age of 55?

I don't know anything about how butts age. I think they just get bigger, right? And I assume they get less supple?

If it helps, Girl B is more likely to get fat than Girl A, or if they both get fat then Girl B will probably be 10 or so pounds bigger.

Thanks. It's hard to get answers to these questions without being called a jerk or a troll, but sexual attraction is important in a relationship (especially currently, since I'm a 26 year old guy), and if I'm going to marry someone I want to know what I'm likely siging up for.

I understand that choosing a person is mostly about who that person is, and not what her body is like, which is why I want you to assume that everything else is equal except for the bodies.

Edit: TL;DR: What ages better, boobs or butt?