Neither really. Our girls are 2 1/2 years apart, so not a big age difference. I used to go for the same number of gifts since that was what the girls noticed. However, a few years ago, my oldest started asking for more expensive things. Actually, it got to where she would only ask for 1 or 2 things, but they were expensive, and my youngest would ask for many things but none of them too expensive. I figured if I was going to keep it even I would have to either not get my oldest the things she really wanted -- opting instead for more, but less expensive ittems that she didn't really want, or up my budget, get her the things she wanted and a few smaller items that I felt certain would never get played with. I didn't want to up my budget plus I was trying to get clutter OUT of my house -- not bring it in. I explained to my oldest that if she wanted those things it was fine but that meant she would have fewer items than her sister. She was fine with that, so she had fewer items, but we actually did spend more $$ on her.
Bottom line.... I try to get them 1 or 2 items they really want. If there is money left over, I will try to get 1 or 2 items that I think they would enjoy. If there is no money left, they don;t get the other things. If I have gotten the extras and still have money left, I don't spend it just for the sake of spending it.