Define best. For me best is Oracle because I've used it for more than 10 years and just a little bit looked in SQL Server. Oracle for me would most probably be faster, more reliable and usable for me because I know how to configure, develop and use various its features. It isn't so with SQL Server so the reason why.

The first thing is to understand that each DBMS is different and what is better for me, won't be better for you and what is better for project X, won't be better for project Y.

It is OK to compare them, but there is one big problem - there are very few people really knowing both of them and really understanding that even if there is not direct mapping for feature X in other DBMS, there are various another ways how to accomplish that.

So ultimate seeking for which is better is useless at least to my mind.