Well, he’d be more prepared for strange things happening to him. At ten, he was only just learning about the supernatural. If he was older, say between sixteen and twenty, he might not have had to live so long without Dean or John.
Based on how they lived, John probably got a cell phone as soon as he could, and would want to keep in touch with his sons. Sam might be able to slip away from Walt and call up his big brother, resulting in them reuniting much earlier on. Dean would have more experience with people the size of his finger, and Sam would trust his brother much faster.
If Sam was cursed as an adult, he’d be even more in tune with Dean. They’d tease each other constantly, and he might be stressed about any thoughts of being stuck that way, but he’d have Dean with him and that’s a much better prospect that being trapped on his own.
Brothers Apart 