The best: Both side are seamed and the hem is sewn over the rough edges on both sides.
Not quite as good: Seamed on both sides and hemmed over one side only?
Both sides are seamed but the hem is seamed as well.
In conclusion, if you want sheets that feel like ours, get:
1. Pima, Supima or Egyptian cotton
2. Percale, (not Sateen)
3. 350-400 thread count
4. Measure your mattress for correct drop/pocket size
5. Get your spouse to iron them!